Question

If an extended object is placed at a distance of 20 cm from a concave mirror of focal length 10

cm, find the image position of it ( Through diagram).

If an extended object is placed at a distance of 30cm from a convex lens of focal length 20 cm,

it’s image position becomes at 55 cm. Find the magnification occurred. Also state the nature of

the image so formed.​

Answer 1

Answer:

It is given that,

Focal length

f=−20cm

hi=3ho

The image is three times the size of the object. So there are two cases.

Case 1. For real image

m=−uv=−3

v=3u

Using mirror’s formula

f1=v1+u1

−201=3u1+u1

u=3−80cm

Case 2. For virtual image

m=u−v=+3

v=−3u

Again using mirror’s formula

−201=−3u1+u1

u=3−40cm

The possible values of u are 3−80cmand3−40cm

Explanation:

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