1. Choose the correct option.
a. The __________ of a mirror is the centre of the sphere of which the mirror is a part.
(i) Centre of curvature (ii) Radius of curvature (iii) Pole (iv) Principal axis
Answer: (i) Centre of curvature
b. Which of the following does not use a concave mirror?
(i) Shaving mirror (ii) Torch light (iii) Car headlight (iv) Rear-view mirror
Answer: (iv) Rear-view mirror
c. A __________ always forms a virtual image.
(i) Plane mirror (ii) Concave lens (iii) Concave mirror (iv) Convex lens
Answer: (i) Plane mirror
2. Assertion–Reasoning questions
a. Assertion (A): A magnifying lens is a concave lens.
Reason (R): A concave lens makes an object look larger.
Answer: Both Assertion (A) and Reason (R) are false.
b. Assertion (A): Silver metal is the best reflector of light.
Reason (R): Silver metal is used to coat one side of mirrors.
Answer: Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
c. Assertion (A): Light reflects only from rough surfaces.
Reason (R): Light reflection may occur from smooth or rough surfaces.
Answer: Assertion (A) is false, but Reason (R) is true.
d. Assertion (A): We can see reflections in mirrors because of regular reflection.
Reason (R): Rough and polished surfaces both reflect light regularly.
Answer: Assertion (A) is true, but Reason (R) is false.
3. Answer the following questions in one sentence.
a. What is reflection of light?
Answer: Reflection of light is the bouncing back of light rays from a surface.
b. What is dispersion of light?
Answer: Dispersion of light is the splitting of white light into seven colours.
c. What is lateral inversion?
Answer: Lateral inversion is the change in the sides of an image in a plane mirror, where the left appears right and the right appears left.
4. Answer the following questions in 2–3 sentences.
a. Compare the principal focus of convex and concave lenses.
Answer: The principal focus of a convex lens is the point where light rays meet after refraction. For a concave lens, the principal focus is the point from which light rays appear to diverge after refraction.
b. Why are concave lenses used in flashlights?
Answer: Concave lenses are used in flashlights to spread light over a larger area by diverging the rays coming from the bulb.
c. We can see reflections of our surroundings on the surface of water in a lake. Why?
Answer: We can see reflections on the surface of water because smooth water acts like a mirror and reflects light regularly.
5. Answer the following questions in 3–4 sentences.
a. How is a real image formed? Give one example of a real image.
Answer: A real image is formed when light rays actually meet after reflection or refraction. It can be formed on a screen. One example of a real image is the image formed on a cinema screen by a projector.
b. What is a concave mirror? What is the nature of image formed by it?
Answer: A concave mirror is a mirror that is curved inward like a spoon. It can form both real and virtual images. When an object is close, it forms a virtual, erect, and magnified image; when it is far, it forms a real and inverted image.