CBSE Class 10 Science Chapter 10 Light-Reflection And Refraction Very Short Answer Questions

CBSE Class 10 Science Light-Reflection And Refraction Very Short Questions and Answers

Question 1. Define the term reflection.
Answer: The bouncing back of light when it strikes a polished surface is called the reflection of light.

Question 2. State the laws of reflection.
Answer:

1. The angle of incidence is equal to the angle of reflection i.e. Li = r.
2. The incident ray, the normal and the reflected ray, all lie in the same plane.

Question 3. What is the radius of curvature of a plane mirror?
Answer: Infinity

Question 4. How will you identify a convex lens by touching it?
Answer: A convex lens is thinner at the center and thicker at the edges.

Question 5. What is the velocity of light in a glass slab with a refractive index of 1.5?
Answer:

v\(=\frac{c}{\mu}=\frac{3 \times 10^8}{1.5}=\)2 × 10⁸ m/s.

Read and Learn More CBSE Class 10 Science Very Short Answer Questions

Question 6. The refractive index of a diamond is 2.42. What is the meaning of this statement about the speed of light?
Answer: It means that light travels 2.42 times faster in a vacuum than in a diamond.

Question 7. For the same angle of incidence, the angle of refraction in three media A, B, and C are 15°, 25°, and 35° respectively. In which medium is the velocity of light minimum?
Answer: In medium C.

Question 8. What will be the focal length of a lens whose power is given as +2.0 D?
Answer:

Given

f = ?, P = + 2.0 D

P = \(\frac{1}{f}\)

⇒ \(\frac{1}{\mathrm{P}}=\frac{1}{2}=0.5 \mathrm{~m}\)

Question 9. Define the term power of a lens.
Answer: It is defined as the ability of a lens to converge or diverge a beam of light falling on it.

Question10. What does positive magnification imply?
Answer: It means that the image formed is erect and virtual.

Question 11. An incident ray falls normally on a glass slab, what is the angle of refraction?
Answer: Zero

Question 12. What type of lens behavior will an air bubble inside water show?
Answer: It will act as a concave lens.

Question 13. What is the expression for the magnification of a lens?
Answer:

⇒ \(m=\frac{-v}{u}\)

Question 14. A thin lens has a focal length of -12 cm. Is it a convex lens or a concave lens?
Answer: Concave lens

Question 15. When the light of 2 colors, A and B is passed through a plane boundary, A is bent more than B. Whcolorlour travels more slowly in the second medium.
Answer: Colour A travels slowly.

Question 16. Between which 2 points related to a concave mirror should an object be placed to obtain on a screen an image twice the size of the object?
Answer: Real image – Between F and C.

Question 17. The speed of light in a transparent medium is 0.6 times that of its speed in a vacuum. What is the refractive index of the medium?
Answer:

⇒ \(n=\frac{c}{v}\)

⇒ \(n=\frac{c}{0.6 c}=\frac{1}{0.6}=1.66\)

Question 18. A person wants a full-length image of a tall building in a small mirror. What type of mirror is used by him?
Answer: Convex mirror

Question 19. Does the value of the speed of light change with the medium?
Answer: Yes, in a denser medium, it becomes less than that in free space.

Question 20. When the angle of incidence is 90°, what is the angle of refraction?
Answer:

n = \(\frac{\sin i}{\sin r}\)

For i = 90°

r = \(\sin ^{-1}\left(\frac{1}{n}\right)\)

Question 21. How does the frequency of a beam of ultraviolet light change when it goes from air into glass?
Answer: Frequency remains the ins same on change of medium.

Question 22. What is the unit of power of a lens?
Answer: Dioptre

Question 23. Give two uses of a convex lens.
Answer:

1. Used in camera.
2. Used in projectors.

Question 24. Mention two properties the the of image formed by a convex mirror.
AnswThe image

1. mage produced is virtuTheimagee mage produced is erect.

Question 25. A lens X has a focal length of 20 cm and a lens Y has a focal length of 40 cm. Which lens would you select to obtain a more convergent beam of light?
Answer: The lens has an ing focal length of 20 cm as it will have more power.

Question 26. the the Can refractive index of a medium be less than unity? What is the value of the refractive index of a vacuum?
Answer: No, because the use speed of light a  in vacuum is maximThe refractivetive index for a vacuum is 1.

Question 27. An object is placed at a distance ‘u’ from the lens of focal length ‘The image is formed at a distance ‘v’ from the lens. Write the relation between u, and v, f.
Answer:

⇒ \(\frac{1}{f}=\frac{1}{v}=\frac{1}{u}\)

Question 28. What is the value of the speed of light in free space?
Answer: L = 3 × 10⁸ m/s

Question 29. Does the refractive index vary with the color of light?
Answer: Yes, (n_v>n_r).

Question 30. What is the importance of the optical center of a lens?
Answer: It signifies the point through which if a light goes, there will not be any direction.