Question

When an object is placed at a distance of 30 cm from a spherical lens, its image is

formed on the wall which is twice the size of the object. At what distance from the lens should the object be placed to obtain a virtual image three times the size of the
object?​

Answer 1

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Physics

Ray Optics and Optical Instruments

Combination of Mirror and Lenses

An object is placed at 30c...

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Asked on December 27, 2019 by

Geeta Tejwani

An object is placed at 30cm from a convex lens and its real image is formed at 20cm away from the lens. Calculate the focal length of convex lens. Draw ray diagram also.

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ANSWER

Here,

Image distance=v=20cm,

Object distance=u=−30cm,

Lens equation is given by,

v

1

−

u

1

=

f

1

,

putting the values we get,

20

1

−

−30

1

=

f

1

,

∴f=12cm

∴ Focal length of convex lens=f=12cm

Explanation:

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