Page 141 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

(b) The image is real.

(c) The image formed by pin hole camera is smaller than the actual object.
(d) The image is sharp if the pinhole is small enough.

E. Short-answer questions.
1. What is the focal length of a spherical mirror?

Ans: It is the distance between the focus & the pole of the spherical mirror.
2. State the relation between radius of curvature and focal length of spherical mirrors.

Ans: If ‘f’ is the focal length and ‘r’ is the radius of curvature, then
r = 2f
r
= f
2

or, Focal length = radius of curvature
2

3. What is the other name for concave lens and a concave mirror?

Ans: The other name for concave lens is diverging lens. The other name for concave mirror
is converging mirror.

4. Differentiate between a real image and a virtual image.
Ans:
Real Image Virtual Image
It can be obtained on a screen. It cannot be obtained on a screen.

Real image is always inverted. Virtual image is always erect.
A real image is formed at a point where A virtual image appears to form at a

light rays intersect or converge. point where reflected rays appear to
meet behind the mirror.

5. Explain a concave mirror with a diagram. What is the nature of image formed by this
mirror?

Ans: A concave mirror is that spherical mirror in which the Silvered
side
reflection of light takes place at the inner surface. In other
words, the reflecting surface of these mirrors is curved Reflecting side
inwards.

It is also known as the converging mirror as the light rays,
after reflection from the mirror, converge or meet at a Concave mirror

point. Spherical mirrors
The nature of the image formed by the concave mirror is virtual erect & diminished.

6. What do you mean by optical medium? State the two types of optical medium.

Ans: An optical medium is a material that allows light to pass though it.

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