Page 165 - NCERT Science Class 10 English Medium

(c) the mirror is concave and the lens is convex.
(d) the mirror is convex, but the lens is concave.
5. No matter how far you stand from a mirror, your image appears erect. The mirror
is likely to be
(a) only plane.
(b) only concave.
(c) only convex.
(d) either plane or convex.
6. 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.
7. 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.
8. Name the type of mirror used in the following situations.
(a) Headlights of a car.
(b) Side/rear-view mirror of a vehicle.
(c) Solar furnace.
Support your answer with reason.
9. One-half of a convex lens is covered with a black paper. Will this lens produce a
complete image of the object? Verify your answer experimentally. Explain your
observations.
10. An object 5 cm in length is held 25 cm away from a converging lens of focal length
10 cm. Draw the ray diagram and find the position, size and the nature of the
image formed.
11. A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far
is the object placed from the lens? Draw the ray diagram.
12. An object is placed at a distance of 10 cm from a convex mirror of focal length
15 cm. Find the position and nature of the image.
13. The magnification produced by a plane mirror is +1. What does this mean?
14. An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex
mirror of radius of curvature 30 cm. Find the position of the image, its nature
and size.
15. An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal
length 18 cm. At what distance from the mirror should a screen be placed, so that
a sharp focussed image can be obtained? Find the size and the nature of the image.
16. Find the focal length of a lens of power – 2.0 D. What type of lens is this?
17. A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of
the lens. Is the prescribed lens diverging or converging?

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