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CBSE Class 8 Science Chapter 6 Reproduction In Animals Short Answer Questions

Question 1. Describe the two modes of reproduction.
Answer: Two modes of reproduction are

Asexual reproduction. It does not involve the fusion of gametes, it results from the multiplication of body cells from a single parent. Daughter cells are identical to the parent. No fertilisation takes place.

Sexual reproduction is characterised by the union of male and female gametes coming from two parents. offspring differ from the parents genetically. Fertilisation takes place

Question 2. It is not necessary to produce a large number of eggs and spores by the animals that reproduce by external fertilisation. Why?
Answer: It is necessary to produce a large number of eggs and sperm by he animals that reproduce by external fertilisation to enhance the chances of fertilisation. As the gametes are released in water, many of them may he carried away by the movement of water, wind, etc., or may be eaten by other aquatic animals, so a large number is released to compensate for the loss.

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Question 3. Mother gives birth to a baby, but the baby has characteristics of both parents. How is this possible?
Answer: Although a mother gives birth to a baby, the baby is formed from the fertilisation of male and female gametes involving two parents. The nuclei of both the parent gametes fuse to form a zygote, thus passing their characteristics to the offspring. This zygote develops inside the female body (uterus) and finally takes birth as a baby

Question 4. Although two cells called gametes fuse, the product formed is a single cell called a zygote. Justify.
Answer: During fertilisation, only the nucleus of the sperm enters the egg cell to form a single-celled structure, which is called a zygote.

Question 5. Can a woman with a blocked Fallopian tube give birth to a baby? How?
Answer: A woman with a blocked Fallopian tube cannot produce babies in the normal way because the eggs released by their ovary cannot meet the sperm and get fertilised in the oviducts. But such women can have babies by using the ‘in vitro fertilisation’ technique.

Question 6. The test-tube babies are called so as they grow inside a test tube. Give your opinion.
Answer: The babies born through the IVF technique are called test-tube babies because the fertilisation takes place in a glass test tube. This is, however, a misleading name as a very brief period is spent in a test tube. After which, the entire growth and development of the baby takes place inside the uterus of the woman as in normal pregnancy.

Question 7. Observe the figure given and answer the questions that follow

Question 8. What happens during the process, and what is formed?
Answer: During the process, the sperm nucleus fuses with the egg nucleus to nun a zygote.

Question 9. The term metamorphosis is not used while describing human development. Why?
Answer: The term ‘metamorphosis’ Is not used while describing human development because in human beings, body parts of an adult arc present from the time of birth llsclf, i.e., while beginning of life as a baby and until you arc an adult, the basic plan of body does not change, On the contrary, in metamorphosis, the parts of the adult arc different from those at the time of birth,.

Question 10. What does the figure represent?

Answer: The figure represents the process of binary fission in Amoeba. During fission, a single Amoeba divides (both nucleus and cytoplasm) to form two daughter cells that develop into two independent Amoeba.

CBSE Class 8 Science Activity: To Observe Budding In Yeast Using Microscope Activities

Aim: To observe the frog eggs

Procedure

1. Visit some ponds or slow-flowing streams during the spring or rainy season.
2. Try to find out clusters of frog eggs floating in water.
3. Note the colour and size of the eggs.

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Observation: We will observe that the colour of the eggs is transparent when unfertilised. If fertilised, a tiny black tadpole appears in the middle. Eggs measure about 2-3mm in size

CBSE Class 8 Science Simple Experiment To Demonstrate Binary Fission With Playdough Amoeba Activity 2

Aim: To collect the eggs of different oviparous animals. Procedure

1. Collect the eggs of as many oviparous animals as possible (e.g. frog, lizard, butterfly, bird, etc).
2. Make drawings of the eggs that you have collected.

Observation: We will observe that the eggs of different oviparous animals are of different colours and sizes.

Conclusion: From this activity, it is concluded that it is easy to collect the egg of oviparous animals because they lay them outside their bodies.

CBSE Egg Fertilization Demonstration Using Balloons And Yarn For Class 8 Science Activity 3

Aim: To study budding in Hydra with the help of permanent slides.

Materials Required: Permanent slide of Hydra, microscope. Procedure

• Get permanent slides of Hydra and observe them using a microscope.
• Look out carefully for any bulges from the parent body.
• Count the number of bulges that you see in different slides.
• Draw the diagram of Hydra as you see it

Observation: We will observe a small single outgrowth or protuberance on the parent body. This bud develops into a tiny individual, which, when fully mature, detaches from the parent body.

Conclusion: From this activity, we can conclude that Hydra reproduces through budding

CBSE Male Reproductive System Parts And Functions Class 8 Explanation Fill In The Blanks

Question 1. Sperms are produced in
Answer: Testes

Question 2. ……Reproduces by budding.
Answer: Hydra

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Question 3. Amoeba is a celled organism…….It reproduces by reproduction. The process of reproduction begins by the devision of The process of reproduction begians by the division of its into two. This is followed by the division of it into two. This type of reproduction is called fission.
Answer: Single, asexual, nucleus, cytoplasm, binary.

Question 4. Reproduction by binary fission occurs in
Answer: Amoeba

Question 5………..reproduces by fragmentation
Answer: Spirogyra

CBSE Metamorphosis In Frogs Stages With Diagram Class 8 Science True Or False

Question 1. All living animals reproduce to produce new young ones.
Answer: True

Question 2. The human egg has a head, middle piece, and tail.
Answer: False, human sperm has a head, middle piece, and tail.

Question 3. Sperms are produced by the ovaries.
Answer: False, sperms are produced by the testes.

Question 4. The male gametes are called sperm.
Answer: False, male gametes are called sperm

Question 5. In adult human females, a single mature egg is released into an oviduct every month
Answer: True

Question 6. Oviparous animals give birth to young ones.
Answer: False, oviparous animals (female) lay eggs

Question 7. Each sperm is a single cell.
Answer: True

Question 8. External fertilisation takes place in a frog.
Answer: True

Question 9.  A new human individual develops from a cell called a gamete.
Answer: False, a new human individual develops from a cell called a zygote

Question 10. An egg laid after fertilisation is made up of a single cell.
Answer: True

Question 11. Amoeba reproduces by budding.
Answer: false, Amoeba reproduces by binary fission

Question 12. Fertilisation is necessary even in asexual reproduction.
Answer: False, fertilisation does not take place in asexual reproduction as no gametes are formed and only a single parent is involved

Question 13. Binary fission is a method of asexual reproduction.
Answer: True

Question 14. A zygote is formed as a result of fertilisation.
Answer: True

Question 15. An embryo is made up of a single cell.
Answer: False, because an embryo is a developing structure formed from a group of dividing cells of a zygote

Question 16. Cows and dogs are viviparous animals.
Answer: True

Question 17. Budding is a method of asexual reproduction.
Answer: True

CBSE DIY Model of Frog Life Cycle for Class 8 Science Project: Match The Columns

Question 1. Match Column 1 with Column 2

Answer: A-3, B-4, C-5, D-1, E-2

Question 10. Match Column 1 with Column 2.

Answer: A-3,B-1,C-4,D-2

CBSE Class 8 Science Chapter 6 – Higher Order Thinking Questions (HOTs) on Animal Reproduction

The following questions consist of two statements: Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below

1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, but R is false
4. A is false, but R is true

Question 1.

Assertion (A) The animals that undergo external fertilisation lay hundreds of eggs.
Reason (R): To enhance the chances of fertilisation.

Answer: 2. Both A and R are true, and R is the correct explanation of A.

Question 2.

Assertion (A) Internal fertilisation occurs in many animals, including humans, cows, dogs, and hens.
Reason (R) Fertilisation, which takes place inside the female body, is called internal fertilisation.

Answer: 2. Both A and R are true, and R is not the correct explanation ofA.

Question 3.

Assertion (A) It is easy to collect the eggs of viviparous animals.
Reason (R) They lay eggs outside their body.

Answer: 4. A is false, but R is true. A can be corrected as it is easy to collect the eggs of oviparous animals

Question 4.

Assertion (A) Human beings do not undergo metamorphosis.
Reason (R) The body parts in adults are not similar to those of babies.

Answer: 3. A is true, but R is false. R can be corrected as the body parts in adults are similar to those of babies

Question 5.

Assertion (A) Binary fission and budding are two methods of asexual reproduction
Reason (R) Only a single parent is involved

Answer: 1. Both A and R are true. R is the correct explanation of A

CBSE Class 8 Science Chapter 2 Microorganisms: Friend And Foe Ncert Folder Intext Questions

Question 1. Pahell saw that her mother added a little curd to warm milk to set curd for the next day. She wonders why?
Answer: Curd contains several microorganisms, including the bacterium Lactobacillus, which promotes the formation of curd. It gets multiplied in the milk and converts it into curd

Question 2. Why are children or infants given vaccinations?
Answer: When vaccines are introduced into a healthy child’s (or person’s) body, the body fights and kills the invading bacteria by producing suitable antibodies. These antibodies remain in the body, and the child is protected from disease-causing microbes.

Read And Learn More CBSE Class 8 Science Question And Answers

Question 3. How do you prevent the spread of communicable diseases?
Answer: We can prevent the spread of communicable diseases by taking some precautions, Examplekeeping a handkerchief on the nose and mouth while sneezing and keeping a distance from infected persons.

Question 4. Why does the teacher keep telling the students not to let water collect anywhere in the neighbourhood?
Answer: We should not let water collect anywhere in the neighbourhood because all mosquitoes breed in the water and spread diseases like malaria.

Question 5. Paheli wonders how food can become a ‘poison’?
Answer: Microorganisms that grow on our food sometimes produce toxic substances, which make the food poisonous, causing serious illness and even death.

Question 6. Why does the milk that comes in packets not spoil? What is pasteurisation?
Answer: The milk that comes in packets does not spoil because it is pasteurised milk. It can be consumed without boiling as it is free from harmful microbes. Pasteurisation is a process in which milk is heated to about 70°C for 15-30 seconds and then suddenly chilled and stored. This prevents the growth of microbes. This process was discovered by Louis Pasteur.

Question 7. Can microorganisms be seen with the naked eye? If not, how can they be seen?
Answer: Microorganisms or microbes are too small to be seen by the naked eye. They can be seen with the help of a magnifying glass or microscope.

Question 8. What are the major groups of microorganisms?
Answer: Microorganisms are divided into four major groups, which are as follows

1. Bacteria are single-celled organisms having a rigid cell wall like plant cells. Diseases like typhoid and tuberculosis (TB) are caused by bacteria.
2. Fungi are non-green organisms that obtain their food from dead organic matter.
3. Protozoa are unicellular animals that cause diseases like malaria and dysentery.
4. Algae are a photoautotrophic organism that may be unicellular or multicellular.

Question 9. Name the microorganisms that can fix atmosphorlc nitrogen in the soil.
Answer: Bacteria such as Rhizobium and certain blue-green algae (Anabaena, Nosloe) present in the soil can fix atmospheric nitrogen and convert it into usable nitrogenous compounds.

Question 10. Write 10 lines on the usefulness of microorganisms in our lives.
Answer: Microorganisms are useful to humans and plants in the following ways

• They are used in the preparation of food items such as pieces of bread.
• Bacteria are used in the conversion of milk into curd.
• They are used for the large-scale production of alcohol, wine, and acetic acid.
• Several medicines, such as antibiotics, are being productÿ by bacteria and fungi.
• They are used to check microbial infections in animals.
• Vaccines are made by dead or weakened microbes.
• Some bacteria and blue-green algae increase the soil fertility by fixing atmospheric nitrogen.
• They decompose the dead organic wastes of plants and animals.
• They are used in the cleaning up of the environment.
• Certain microbes are also used in the biological treatment of sewage and industrial effluents.

Question 11. Write a short paragraph on the harmful effects of microorganisms.
Answer: Microorganisms are harmful to human beings in many ways. They cause diseases in humans, plants and animals. For example, in humans, bacteria cause diseases such as cholera, typhoid, tuberculosis, etc.

In cattle, the foot and mouth disease is caused by a virus. Also, several microbes cause diseases in plants, for  Example, Citrus canker disease, and late blight of potato. Some microbes grow on food and secrete toxic substances which make the food poisonous.

Class 8 Science Chapter 2 Fill In The Blanks

Question 1. Microorganisms can be seen with the help of a __________.
Answer: Microscope

Question 2. Blue-green algae fix ________directly from the air and enhance the fertility of soil.
Answer: Nitrogen

Question 3. Alcohol is produced with the help of _________.
Answer: Yeast

Question 4. Cholera is caused by ________.
Answer: Bacteria

Question 5. All microorganisms are classified into major ______ groups.
Answer: Four

Question 6. Paramecium is a slipper-shaped _____.
Answer: Protozoan

Question 7. Alexander Fleming discovered mould _______.
Answer: Penicillin

Question 8. Pathogens are ________ causing organisms.
Answer: Disease

Question 9. ______ could be due to the consumption of food spoiled by some microorganisms
Answer: Food Poisoning

Question 10. The process in which sugar is converted into alcohol is called __________.
Answer: Fermentation

Question 11. _________is a process of heating the milk at high temperature, then cooling it suddenly and storing it.
Answer: Pasteurisation

Question 12. ___________ is the vector of the dengue virus
Answer: Aedes

Class 8 Science Chapter 2 True Or False

Question 1. Microorganisms can be seen with the naked eye.
Answer: False, microorganisms are very small and cannot be seen by nthe aked eye. They can be seen with the help of a microscope.

Question 2. Microorganisms can be found only in air and water.
Answer: False, microorganisms are found everywhere in the air, water, inside our body, etc.

Question 3. Viruses can only multiply in a living cell.
Answer: True

Question 4. All microbes are disease-causing.
Answer: False, some microbes are useful, for example, Lactobacillus.

Question 5. Microorganisms are also used in the cleaning up of the environment.
Answer: True

Question 9. Jams, jellies and squashes are preserved by adding salt.
Answer: False

Question 10. The atmospheric nitrogen cannot be utilised by the living organisms.
Answer: True

Question 11. Viruses can be seen by simple microscopes.
Answer: False

CBSE Class 8 Science Chapter 2 Match The Columns

Question 1. Match the microorganisms given in Column 1 to the group to which they belong in Column 2.

Answer: A-4, B-3, C-1, D-2

Question 2. Match the Items given In Column 1 with those of Column 2

Answer: A-4, B-5, C-1, D-2, E-3

Question 3. Match the names of scientists given in Column 1 with the discovery made by them given in Column 2.

Answer: A-3, B-2, C-4, D-1

Question 4. Match the organisms in Column A with their action in Column B.

Answer: A-(5), B-(1), C-(2), D-(3), E-(4), F-(5)

Question 5. Match Column I with Column II.

Answer: A-6, B-5.C-7, D-4, E-3, F-2.G-1

Class 8 Science Chapter 2 Microorganisms: Friend And Foe

The following questions consist of two statements: Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below

1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false
4. A is false, but R is true.

Question 1.

• Assertion (A) Lactobacillus converts curd into milk.
• Reason (R) The conversion of milk into curd is known as fermentation.

Answer: 4. A is false, but R is true. A can be corrected as Lactobacillus converts milk into curd.

Question 2.

• Assertion (A) Streptomycin and tetracycline are examples of antibiotics.
• Reason (R) Antibiotics help in the growth of disease-causing microorganisms.

Answer: 3. A is true, but R is false. R can be corrected as Antibiotics are the medicines that kill or stop the growth of disease-causing microorganisms.

Question 3.

1. Assertion (A) Sodium benzoate and sodium metabisulfite are common preservatives.
2. Reason (R) They are used to control the growth of microbes.

Answer: 1. Both A and R are true, and R is the correct explanation of A.

Question 4.

1. Assertion (A) Pasteurised milk cannot be consumed without boiling.
2. Reason (R) Pasteurised milk is free from microorganisms.

Answer: 4. A is false, but R is true. A can be corrected as Pasteurised milk can be consumed without boiling.

Question 5.

1. Assertion (A) Rhizobium is an example of a nitrogen-fixing bacterium.
2. Reason (R) This bacterium converts nitrogen compounds into nitrogen gas.

Answer: 3. A is true, but R is false. R can be corrected as Rhizobium bacteria convert nitrogen gas into nitrogenous compounds, which are utilised by plants.

The following questions consist of two statements: Assertion (A) and Reason (R); Answer these questions by selecting the appropriate option given below.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false.
4. A is false, but R is true

Question 1.

1. Assertion (A) Antibiotics are effective against cold and flu
2. Reason (R) Cold and flu are caused by a virus.

Answer: 4. A is false, but R is true

Question 2.

1. Assertion (A): Decomposers clean the environment.
2. Reason (R) They decompose the harmful dead and decaying remains of plants and animals.

Answer: 1. Both A and R are true, and R is the correct explanation of A.

CBSE Class 8 Science Chapter 13 Light Multiple Choice Questions

Question 1. We can see a non-luminous object when light

1. Emitted by the object falls on the eye
2. Is reflected from the object towards our eye
3. Completely passes through the object
4. Gets completely absorbed by the object

Answer: 2. Is reflected from the object towards our eye

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Question 2. Angle of incidence is equal to the angle of reflection.

1. Always
2. Sometimes
3. Under special conditions
4. Never

Answer: 1. Always

Question 3. Image formed by a plane mirror is

1. Virtual, behind the mirror and enlarged
2. Virtual, behind the mirror and of the same size as the object
3. Real at the surface of the mirror and enlarged
4. Real, behind the mirror and of the same size as the object

Answer: 2. Virtual, behind the mirror and of the same size as the object

Question 4. Which of these objects reflects light?

1. The sun
2. The moon
3. A glowing bulb
4. Burning wood

Answer: 2. The moon

Question 5. A tiny mirror Mis fixed on a piece of cardboard placed on a table. The cardboard is illuminated by light from a bulb. The position of eye with respect to position of bulb is shown in figure as A, B, C and D. In which position, mirror will be visible?

1. A
2. C
3. B
4. D

Answer: 1. A

Question 6. Two mirrors A and B are placed at right angles to each other as shown In figure.

A ray of light incident on mirror A at an angle of 20° falls on mirror Bafter reflection. The angle of reflection for the ray reflected from mirror B would be

1. 25°
2. 70°
3. 50°
4. 115°

Answer: 2. 70°

Question 7. A small hole P Is made In a piece of cardboard. The hole Is Illuminated by a torch as shown in figure. The pencil of light coming out of the hole falls on a mirror

At which point should the eye be placed so that the hole can be seen?

1. A
2. B
3. C
4. D

Answer: 1. A

Question 8. Light is falling on surfaces Si, % S3 as shown in figure.

Surfaces on which the angle of incidence is equal to the angle of reflection is/are

1. Only S1
2. S1 and S2
3. S2 and S3
4. All the three surfaces

Answer: 4. All the three surfaces

Question 9. As the angle between two plane mirrors is decreasing gradually, the number of Images of an object placed between them

1. First increases then decreases
2. First decreases then increases
3. Increases
4. Decreases

Answer: 3. Increases

Question 10. How does the eye change To focus on near or distant objects?

1. The eye lens moves in or out
2. The retina moves in or out
3. The eye lens becomes thicker or thinner
4. The pupil becomes larger or smaller

Answer: 3. The eye lens becomes thicker or thinner

CBSE Class 8 Science Chapter 13 Long Answer Type Questions

Question 1. Them Is n mistake in each of the following ray diagrams given ns figure (a), (b). and (c). Make the necessary correction (s).

Answer: The correct diagrams are as below

Question 2. A man stands 10 m in front of a large plane mirror, so how far must he walk before he is 5 m away from his image?
Answer: As, per the given information, point 0 is initial position of the man and I is initial position of the image of the man can be show with the help of a figure.

Point O’ is final position of the man and I’ is final position of the image of the man. From the figure.

O’P + PI’ = 5m [0’P = PI’]

0’P + 0’P = 5m

0’P = 25m

Distance walked by the man = OP- O’P
= 10-2.5 = 7.5m

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Question 3. Aditya visited a lake on two days. On the first day, the reflection of the surrounding mountains could be seen clearly in water of the lake. On the second day, he was not able to see the reflection of the mountains clearly. Give one possible reason for this phenomenon and explain your answer clearly.
Answer: The unclear image of the mountains on the second day is probably due to wind blowing across the lake causing it to lose its calmness. When the lake is calm, the surface of the lake is smooth and regular reflection occurs, allowing a clear image of the mountains to be formed. When the wind blows across the lake, the surface of the lake becomes rough and uneven causing a diffused reflection, lienee, the image formed of the mountains will be unclear and blurred.

Question 4. Figure shows tho word REST written In two ways In front of a mirror. Show how the word would appear In the mirror?

Answer: According to reflection properties of plane mirror, it forms same size, laterally inverted images of the object infront of them.

Question 5. Boojho planned an activity to observe an object A through pipes as shown in figure, so that he could see objects which he could not directly see.

1. Mention how many mirrors should he use to see the objects?

Answer: Number of mirrors = 3

2. Indicate the positions of the mirrors in the figure.

Answer: Positions of the mirrors are as shown in figure

3. State what must be the angle w.r.t. the incident  light at which he should place the mirrors?

Answer: Mirrors should be placed at 45° w.r.t. the incident light, so that ray can move forward.

4. Indicate the direction of rays in the figure of (2) Part.

Answer: Direction of rays is shown in figure.

5. If any of the mirrors is removed, will he be able to see the objects?

Answer: He will not be able to see the objects ifany of the mirrors is removed, since he will not get the rays after that removed mirror.

CBSE Class 8 Science Chapter 13 Light Short Answer Type Question

Question 1. Look at figure. Can the Image of the child In It be obtained on a screen?

Answer: The image of the child cannot be obtained on the screen because the image is not real. The images formed by plane mirror are virtual, so these virtual images cannot be seen on die screen.

Question 2. What is the difference between the surfaces of a sheet of sandpaper and a mirror?

Answer: The sandpaper has a rough surface causing light that is reflected on it to be scattered at different angles. The mirror however, allows regular reflection. Sandpaper cannot produce any image, unlike the mirror due to diffused (irregular) reflection.

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Question 3. Explain how do we see various objects?

Answer: Due to reflection, we can see various objects. Since, we know that, all surfaces reflect light So when light falls on them (any objects), it reflects the light. In this way, this reflected light enters our eyes and due to this, we can see the object.

Question 4. Draw figure showing the position of the plane mirror. Also, label the angle of incidence and angle of reflection on it.

Answer:

Question 5. “The laws of reflection only holds true for regular reflection”. Is this statement true or false? Explain your answer.
Answer: False, the laws of reflection holds for both regular and diffused reflection. In a diffused reflection, the reflecting surface being rough anil uneven, the parallel beam of light is reflected in different directions and angles.

Question 6. Explain what happens to light when It gets dispersed?Also, give an example.
Answer: Light is splitted into its constituent colours (7 colours) when it gets dispersed, e.g. rainbow formation is due to the dispersion of white light after passing through water droplets.

Question 7. Which part of the eye gets affected, if someone is suffering from cataract? How is it treated?
Answer: In people suffering from cataract, the eye lens becomes cloudy. Cataract is treated by replacing the convex lens with a new artificial lens.

Question 8. Eyes of the nocturnal birds have large cornea and a large pupil. How does this structure help them?
Answer: The size of the eyes of nocturnal bird is large. Large eyes with a wider pupil, larger lens and increased retinal surface can collect more ambient light which help them to see the objects even at night easily. 

Question 9. “Though the image formation on retina is inverted but still we are able to see the erect objects”. Explain how?
Answer: Yes, it is very true to say because the formation ofimage on the retina is conveyed to brain in the form ofelectrical impulses with the help ofoptical nerves. So, brain is able to perceive an erect image ofobject with the help of electrical impulses.

Question 10. Explain in brief, how do ciliary muscles affect the functioning of eye?
Answer: As we know that, ciliary muscles can contract and relax, because of it, this can change the shape of eye lens which results in change in its focal length. So, eye lens can make image of nearby objects and also far off objects on retina.

Question 11. The picture shows the size of the pupil under two different conditions.

What makes the pupil change size between conditions 1 and 2?

Answer: In condition 1, eyes get insufficient amount oflight. That’s why, the pupil expands but in condition 2, eyes get large amount of light that’s why pupil contract.

Question 13. Boojho stands at A just on the side of a plane mirror as shown In figure. Can he see himself in the mirror ? Also, can he see the image of objects situated at P, Q and R?

Answer: As Boojho is not in the range of reflecting surface rather, he is standing away from the mirror, so he cannot see himself in the mirror. But he can see the image ofP which is in the reflecting area but not ofQ and R.

Question 14.

1. Find out the position of the Image of an object situated at A In the piano mirror.
2. Can Pahell at B see this Imago?
3.  Can Boojho at C see this Image?
4. When Pahell moves from B to C, where does the Image of A move?

Answer:

1. Since, it is plane mirror, so the image is formed behind the mirror and there is a lateral inversion in it

1. Yes, Paheli can see the image of object A.
2. Yes, Boojho can also see the image of object A.
3. No change in the position of the image of A

CBSE Class 8 Science Chapter 13 Light Very Short Answer Questions

Question 1. Why are we able to see the tap water in the glass even though It Is colourless?
Answer: Tap water reflects the light into our eyes. As long as an object reflects light into our eyes, we can see it.

Question 2. Light travels fastest in a vacuum. Why?
Answer: Light travels faster in a vacuum than in any other medium because there is no obstruction to the passage of light in a vacuum.

Read And Learn More CBSE Class 8 Science Very Short Questions And Answers

Question 3. Mention the five English letters that do not show lateral inversion on suffering reflection from a plane mirror.
Answer: The five English letters that do not show the lateral inversion on suffering reflection are A, H, O, T, and U.

Question 4. How many times is ray of light reflected by two plane mirrors placed parallel and facing each other?

Answer:

The ray is reflected infinitely between the two plane mirrors placed parallel to each other.

Question 5. The angle between the incident ray and the reflected ray is 60 0. What is the value of the angle of incidence?

Answer: Since the angle of incidence = the angle of reflection. So, angle of incidence = 30°

Question 6. Imagine that parallel rays are incident on an irregular surface. Are the rays reflected from this surface parallel to each other?
Answer: No, the reflected rays from an irregular surface are in different directions.

Question 7. When a parallel beam of light hits an uneven surface, predict the nature of the reflected beam.

Answer: When light hits an uneven surface, there are many angles of incidence. Hence, the parallel beam of light rays will be reflected off the surface at different angles,

Question 8. State the size of the image formed by a plane mirror.
Answer: The size of the image formed by a plane mirror is the same as that of the object in front of the mirror.

Question 9. Mention the name of the device that is generally used by the designers of wallpapers and fabrics.
Answer: A Kaleidoscope is a device that is generally used by the designers of wallpapers and fabrics.

Question 10. White light is a combination of which colours?
Answer: White light is a combination of seven colours, which are Violet, Indigo, Blue, Green, Yellow, Orange, and Red.

Question 11. A safety vest helps to keep workers working by the roadside safe. This is especially so during the benight. Why?
Answer: The reflectors on the safety vest reflect light into the motorist’s eyes. This helps to alert the motorists to the wearer’s presence on the road.

CBSE Class 8 Science Chapter 10 Sound Very Short Answer Questions

Question 1. Does any part of our body vibrate when we speak? Name the part.
Answer: Yes, while speaking, the part that vibrates is called the vocal cords. It is below the throat and creates vibrations while speaking.

Question 2. Explain how you can describe vocal cords.
Answer: The two ligaments which stretch across the larynx in such a way that it leaves a narrow slit between them for the passage ofair, are known as vocal cords.

Read And Learn More CBSE Class 8 Science Very Short Questions And Answers

Question 3. Name two musical instruments that produce sound by vibrating strings.
Answer: The Guitar and sitar are two musical instruments that produce sound by vibrating strings.

” Cbse Class 8 Science Chapter 10 Vsaqs “

Question 4. Why do we not hear the sound of an explosion on the surface of the moon?
Answer: There is no atmosphere on the moon, and sound waves need a medium to travel, so we cannot hear sound on the moon.

Question 5. How do whales and dolphins hear sound?
Answer: Through water as a liquid medium, both whales and dolphins hear the sound

Question 6. When we hear a sound, does any part of our body
Answer: It is the eardrum that vibrates and sends vibrations to the inner ear when we hear any sound.

” Sound Very Short Answer Questions Class 8 “

Question 7. A baby recognises her mother by her voice. Name the characteristic of sound involved.
Answer: Pitch is that characteristic of sound by which distinction can be made between two sounds.

Question 8. What is the frequency of a wave with a period of 0.025 s?
Answer: Given, T =0.025 s,

⇒ \(\mathrm{v}=\frac{1}{T}=\frac{1}{0.025}=40 \mathrm{~Hz}\)

” Sound Propagation Through Medium “

Question 9. Different bees produce buzzing sounds of different pitches. Which affects the pitch of the bee’s buzzing sound?
Answer: The faster the bee vibrates its wings, rthe greater the frequency of the sound and the frequency of sound. Hence, the higher the frequency, the more will he the pitch.

Question 10. Our steps do not produce a loud sound if we walk on a carpet floor. Explain with the help of a reason.
Answer: As the amplitude of vibrations of the floor is reduced and the sound ot our steps becomes feeble, so due to this reason, we do not produce a loud sound when we walk on a dry carpet floor.

” Vocal Cords And Sound Production “

Question 11. Mention the name given to the maximum displacement of a vibrating body from its central position.
Answer: Amplitude is a name given to the maximum displacement of a vibrating body from its central position.

Question 12. Explain why babies have a feeble sound.
Answer: Due to the small amplitude of their sound, babies have a teething sound

Question 13. Three different vibrating objects produce three types of sounds, X, V, and Z. The sounds X and Y cannot be heard by a man having a normal range of hearing, but sound Z can be heard easily. The sound X can be heard by a bat, whereas sound Y can be heard by a rhinoceros. What type of sounds are X, Y, and Z?
Answer: X is ultrasonic sound, Y is infrasonic sound, and Z is audible sound.

” Musical Instruments With Vibrating Strings “

Question 14. Lightning can be seen at the moment when it occurs. Paheli observes lightning in her area. She hears the sound 5 s after she observed lightning. How far is she from the place where lightning occurs? (Speed of sound =330 m/s)
Answer: We know that,

• Distance = Speed x Time = 330 x 5 =1650 m
• = 1.65 km (Y 1 km =1000 m)
• So, she is standing 1.65 km from the place where the lightning occurs.

Question 15. A hearing aid that is attached to the ear helps people who suffer from hearing loss. What is the main function of the hearing aid?
Answer: The hearing aid amplifies the sound received from the surroundings.

CBSE Class 8 Science Chapter 13 Light Activities Activity 1

Aim To understand the reflection by a plane mirror.

Material Required Drawing board, white sheet, comb, plane mirror, black paper, and a torch.

Procedure

1. Fix the white sheet of paper on the drawing board.
2. Take the comb and close all its holes except one present in the middle with the help of black paper.
3. Hold the comb perpendicular to the drawing board.
4. Now, take the torch and throw light on the comb. Light must fall on the opening of the comb.
5. 5. You will see a ray of light falling on the drawing board. Place a plane mirror in the path of light and observe what happens to the ray coming from the comb.

Conclusion The light ray strikes with the mirror and changes its path. The ray coming from the comb is incident ray and the ray going after striking the mirror is reflected ray.

Read And Learn More CBSE Class 8 Science Activities

CBSE Class 8 Science Second Law Of Reflection Activity 2

Aim To understand the second law of reflection.

Material Required A chart paper (white) , a plane mirror, a comb, black paper and a torch.

Procedure

1. Spread the white chart paper on the table such that it extends little beyond the edge of the table.
2. Close all the holes of the comb with black paper, except one at the middle.
3. Place plane mirror and comb perpendicular to the table as shown
4. You will see the incident ray and reflected ray on the while chart paper. Now, bend the chart paper at the end of the table.
5. You will not see the reflected ray on the bended portion of the chart paper. Now, bring the paper back to its original position. You will again see the reflected ray.

Conclusion We have concluded that the incident ray, reflected ray and the normal all lie in the same plane.

CBSE Class 8 Science Formation Of Image By A Plane Mirror Activity 3

Aim To study the formation of image by a plane mirror.

Material Required Drawing board, a white paper, a plane mirror, a pencil and a ruler.

Procedure

1. Paste the white paper on the drawing board.
2. Consider that an object is at O. Now, draw two rays OM and OH incident on the mirror.
3. Draw two reflected rays MN and HG by making angle of reflection equal to angle of incidence. Extend these reflected rays further. You will find that they do not meet.
4. Now, extend the two reflected rays using a pencil and ruler behind the mirror (dotted lines). Mark the point 1 where they meet.
5. Since, the reflected rays do not actually meet at 1, we say that it is a virtual image.
6. Measure the distance of object (PO) and distance of image (PI) from the mirror (PQ).

Conclusion

1. The distance of object from the mirror is same as the distance ofthe image from the mirror i.e. PO = PI.
2. The image formed by plane mirror is virtual.

CBSE Class 8 Science Properties Of Reflection From An Irregular Surface Activity 4

Aim To study the properties of reflection from an irregular surface using laws of reflection.

Material Required White sheet, ruler, protractor and a pencil.

Procedure

1. Drawa rough surface on the white sheet as shown in figure (a).

1. Draw parallel rays which fall on this surface. These rays arc incident rays.
2. Draw perpendicular line at every point of incident on the surface.
3. Now, measure the angle between normal and incident ray for every ray. This is angle of incidence.
4. Draw angle of reflection which is equal to the angle of incidence as shown in figure (b), then draw reflected rays.

Conclusion Incident rays are parallel but reflected rays are not parallel. Hence, irregular surfaces produce irregular or diffused reflection.

CBSE Class 8 Science Number Of Images Formed By Two Mirrors Activity 5

Aim To study the number of images formed by two mirrors inclined at some angle.

Material Required Two mirrors, any small object like pen, pencil or rubber.

Procedure

• Place two mirrors at right angles to each other with their edges touching.
• Place the object in between the mirrors. We can see two images in the mirrors.

• Now, change the angle between mirrors (like 45°,60°,120°,180°). You can set angles with the help of a protractor.
• Note down the number of images formed in each case.

Conclusion

1. When angle between mirrors is greater than 90°, then two Images are formed.
2. When the angle between mirrors is less than 90“, then number of images increases.

CBSE Class 8 Science Build A Kaleidoscope Activity 6

Aim To build a kaleidoscope.

Material Required Three rectangular mirror stripes (15 cmx 4 cm), circular cardboard tube, cardboard disc, a circular transparent glass plate, a circular grounded glass plate and several small pieces ofcoloured glass or bangles.

Procedure

1. Take the three rectangular mirror strips and join them to form a hollow prism with their reflecting surface facing each other.
2. Fix this prism in a circular cardboard tube and close one end of the tube by a cardboard disc. Make a small hole in this disc.
3. Close the other end of prism with the circular glass plate.
4. Put several pieces of coloured bangles on this plate.
5. Close the end oftube with the grounded circular glass plate. Now, your kaleidoscope is ready.
6. Now, see through the hole and rotate the cardboard

Conclusion We observed different patterns in the kaleidoscope every time. These patterns are visible due to multiple reflection by glass strips.

Activity 7

Aim To show that sunlight is made up of seven colours.

Material Required A howl filled with water, a plane strip of mirror, white paper.

Procedure

1. Place the howl filled with water on a table. Now, place a strip of mirror partially immersed into the water.
2. Place this arrangement near a window such that direct sunlight falls on the mirror.
3. Adjust the mirror in such a way that the reflected light fall on a wall.
4. Place the white paper where the reflected light fall on the wall.
5. Observe the colours of reflected light.

Conclusion Sunlight is made up ofseven colours named as violet,indigo, blue, green, yellow, orange and red. In short form, it is known as VIBGYOR (first letter ofevery colour) and the splitting of light into its constituent colours is known as dispersion of light.

CBSE Class 8 Science The Effect Of Light Activity 8

Aim To observe the effect of light on the size of pupil.

Material Required A torch.

Procedure

1. Look into your friends eye and observe the size of pupil.
2. Now, throw light on her eye with the torch. Now, observe the size of pupil.
3. Now, switch OFF the light and observe the size of pupil once again.

Conclusion

1. Size of pupil is small when the torch is ON. This happens to protect eye from intense light.
2. Size ofpupil increases when the torch is switched off. This happens to gather more light to see objects clearly.

CBSE Class 8 Science Existence Of Blind Spot Activity 9

Aim To demonstrate the existence of blind spot in the eye.

Material Required A white paper strip and a marker.

Procedure

1. Make a round mark and a cross mark on a sheet of paper with the help of marker. The round mark should be or the right side of the cross mark.
2. Distance between the two marks should be 6-8 cm.
3. Now, hold this paper at an arm’s length from the eye.
4. Close your left eye and look continuously on the cross mark.
5. Move the sheet slowly towards your eye and keep your eye on the cross.
6. Move the sheet towards your eye until the round mark disappears.
7. Now, close your right eye and look at the round mark, then repeat step 5 and 6

Conclusion While bringing the strip towards the eye at some point, one mark disappears.

CBSE Class 8 Science The Persistence Of Vision Activity 10

Aim To understand the persistence of vision.

Material Required A square piece of cardboard, a long thread and a pencil.

Procedure

1. Make two holes in the cardboard as shown in figure.
2. Draw a cage on one side of the cardboard and a bird on the other side of the cardboard.
3. Now, insert the string in the hole as shown in the diagram.
4. Now, hold the free ends of the thread on both sides and twist it in such a way that the cardboard rotates very fast. Now, write your observation.

Conclusion The bird appears as it is in the cage but it is on the other side of the cardboard.