Question

how far should be an object be placed for a convex lens of focal length 20cm to obtain its image at a distance of 30 cm from the lens what will be the height of the image if the object is 6cm tall​

Answer 1

Answer:

Object distance = 60cm

Magnification =0.5

Explanation:

Use 1/f=1/v+1/u ,all distances in SI system

magnification = -v/u

Answer 2

Answer:

Your answer is below

Explanation:

v=30cm

u=?

f=20cm

1/v-1/u=1/f

1/v-1/f=1/u

1/30-1/20=1/u

1/u=1/60

U=-60

The objest should be placed at 60cm.

M=v/u

M=30/-60

M=-0.5

M=hi/ho

Using (1)

-0.5=hi/6

hi=-3

Height of image will be 3cm.

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