Page 140 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

7. In irregular reflection, a parallel beam of light rays falls on a smooth and polished

surface and reflects back in a parallel manner.
8. The focal length and the center of curvature of a convex mirror is virtual in nature.

9. Sir Issac Newton discovered the telescope.
10. The radius of curvature of the spherical mirror is twice the focal length.

Ans: 1. (F) 2. (F) 3. (F) 4. (T) 5. (F) 6. (F) 7. (F) 8. (T) 9. (F) 10. (T)
D. Very short-answer questions.

1. Write the laws of reflection.
Ans: The incident ray, the reflected ray and the normal at the point of incidence, all lie in

the same plane.
The angle of incidence (∠i) and the angle of reflection (∠r) are always equal, that is,

∠i = ∠r.
2. Why is the word ‘AMBULANCE’ written left to right in an inverted manner on the

vehicle?
Ans: The word 'AMBULANCE' is written left to right in an inverted manner so that due to

lateral invversion, its image gets inverted & appears erect in the rear-view mirror of
the vehicle ahead of the ambulance. So the ambulance can pass easily through the

traffic.
3. State the uses of a concave mirror.

Ans: • Dentists use a concave mirror to reflect light on a particular tooth.
• Shaving mirrors are concave mirrors to get a magnified image.

4. What makes things visible to us?
Ans: Light energy makes things visible to us.

5. Define bioluminescence. Give an example.
Ans: Certain living organisms can emit light due to a chemical reaction that takes place

in the body in which chemical energy is converted in to light energy. This is called
bioluminescence. For example, firefly, glow worm, lantern fish, etc.

6. State the characteristics of the image formed in the plane mirror.
Ans: Characteristics of image formed in the plane mirror:

• The image formed is virtual and erect.
• The image is of the same size as that of the object.

• The image always forms at the same distance behind the mirror as it in the
front.

7. State the characteristics of the image formed in the pin hole camera.
Ans: Characteristics of image formed in the pin hole camera:

(a) The image is inverted

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