A concave lens has focal length 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.

Given: The image distance, v = - 10 cm The focal length, f = - 15 cm From the lens formula, 1 f = 1 v - 1 u ⇒ 1 - 15 = 1 - 10 - 1 u ⇒ 1 u = - 1 30 ⇒ u = - 30 cm The object should be placed at 30 cm from the concave lens. The magnification, m = v u = - 10 - 30 = + 0 . 33 The magnification produced by the lens is + 0 . 33 .

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10th CBSE

IMPORTANT

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Calculate the focal length of a convex lens which produces a virtual image at a distance of $50 cm$ of an object placed $20 cm$ in front of it.

Important Questions on Refraction of Light

EASY

10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Short Answer Type Questions>Q 13

An object is placed at a distance of $100 cm$ from a converging lens of focal length $40 cm$ .

What is the nature of the image?

EASY

10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Short Answer Type Questions>Q 13

An object is placed at a distance of $100 cm$ from a converging lens of focal length $40 cm$ .

What is the position of the image?

HARD

10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Short Answer Type Questions>Q 14

A convex lens produces an inverted image magnified three times of an object placed at a distance of

15 cm

from it. Calculate focal length of the lens.

HARD

10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Short Answer Type Questions>Q 15

A converging lens of focal length

5 cm

is placed at a distance of

20 cm

from a screen. How far from the lens should an object be placed so as to form its real image on the screen?

HARD

10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Short Answer Type Questions>Q 16

An object

5 cm

high is held

25 cm

away from a converging lens of focal length

10 cm

. Find the position, size and nature of the image formed. Also draw the ray diagram.

MEDIUM

10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Short Answer Type Questions>Q 17

At what distance should an object be placed from a convex lens of focal length

18 cm

to obtain an image at

24 cm

from it on the other side? What will be the magnification produced in this case?

HARD

10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Short Answer Type Questions>Q 18

An object

2 cm

tall is placed on the axis of a convex lens of focal length

5 cm

at a distance of

10 m

from the optical centre of the lens. Find the nature, position and size of the image formed. Which case of image formation by convex lenses is illustrated by this example?

HARD

10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Short Answer Type Questions>Q 19

The filament of a lamp is

80 cm

from a screen and a converging lens forms an image of it on a screen, magnified three times. Find the distance of the lens from the filament and the focal length of the lens.

Calculate the focal length of a convex lens which produces a virtual image at a distance of 50 cm of an object placed 20 cm in front of it.

Important Questions on Refraction of Light

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Calculate the focal length of a convex lens which produces a virtual image at a distance of $50 cm$ of an object placed $20 cm$ in front of it.