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 .

E M B I B E

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Long Answer Type Questions>Q 30

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10th CBSE

IMPORTANT

Earn 100

State whether concave lens has a real focus or a virtual focus.

Important Questions on Refraction of Light

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10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Long Answer Type Questions>Q 30

List some things that concave lens and convex mirror have in common.

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10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Long Answer Type Questions>Q 31

Draw ray diagrams to represent the nature, position and relative size of the image formed by a convex lens for the object placed:

(a) At $2 F_{1}$ ,

(b) Between $F_{1}$ and the optical centre $O$ of the lens.

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10th CBSE

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Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Long Answer Type Questions>Q 32

An object is placed well outside the principal focus of a convex lens. Draw a ray diagram to show how the image formed, and say whether the image is real or virtual.

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10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Long Answer Type Questions>Q 32

What is the effect on the size and position of the image of moving the object towards the lens.

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10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Long Answer Type Questions>Q 32

What is the effect on the size and position of the image on moving the object away from the lens?

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10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Long Answer Type Questions>Q 33

Explain what is meant by a virtual, magnified image.

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10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Long Answer Type Questions>Q 33

Draw a ray diagram to show the formation of a virtual magnified image of an object by a convex lens. In your diagram, the position of object and image with respect to the principal focus should be shown clearly.

HARD

10th CBSE

IMPORTANT

Science for Tenth Class Part - 1 Physics>Chapter 5 - Refraction of Light>Long Answer Type Questions>Q 33

Three convex lenses are available having focal lengths of