Prism Academy
Subject: Science 10th CBSE
Chapter: Light – Reflection and Refraction (Test I)
Total Marks: 30
Q.1. Answer the following. (ONE mark each)
1) Define the principal focus of a concave mirror.
2) A ray of light travelling in air enters obliquely into water. Does the light ray bend
towards the normal or away from the normal? Why?
3) Define 1 dioptre of power of a lens.
4) No matter how far you stand from a mirror, your image appears erect. The mirror is
likely to be
(a) Plane. (b) Concave. (c) Convex. (d) Either plane or convex.
5) Name the type of mirror used in the Headlights of a car.
6) Where should an object be placed in front of a convex lens to get a real image of the
size of the object?
(a) At the principal focus of the lens
(b) At twice the focal length
(c) At infinity
(d) Between the optical centre of the lens and its principal focus.
7) Which of the following lenses would you prefer to use while reading small letters found
in a dictionary?
(a) A convex lens of focal length 50 cm.
(b) A concave lens of focal length 50 cm.
(c) A convex lens of focal length 5 cm.
(d) A concave lens of focal length 5 cm.
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8) A ray of light AM is incident on a spherical mirror as shown in the diagram.
Redraw the diagram on the answer sheet and show the path of reflected ray.
Q.2. Answer the following
1. Two lenses have power of (i) + 2D (ii) - 4D. What is the nature and focal length (in cm)
of each lens? [3]
2. Light enters from air to glass having refractive index 1.50. What is the speed of light in
the glass? The speed of light in vacuum is 3 × 108 m s–1. [3]
3. A concave mirror produces three times enlarged image of an object placed at 10 cm in
front of it. Calculate the radius of curvature of the mirror. [3]
4. A concave lens has focal length of 15 cm. At what distance should the object from the
lens be placed so that it forms an image at 10 cm from the lens? Also, find the
magnification produced by the lens. [3]
5. A 2.0 cm tall object is placed perpendicular to the principal axis of a convex lens of focal
length 10 cm. The distance of the object from the lens is 15 cm. Find the nature, position
and size of the image. Also find its magnification. [3]
6. We wish to obtain an erect image of an object, using a concave mirror of focal length
15 cm. What should be the range of distance of the object from the mirror? What is the
nature of the image? Is the image larger or smaller than the object? Draw a ray diagram
to show the image formation in this case. [5]
7. A convex lens forms a real and inverted image of a needle at a distance of 50 cm from
it. Where is the needle placed in front of the convex lens if the image is equal to the size
of the object? Also, find the power of the lens. [2]
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