Question

9. An object 4 cm high is placed at a distance of 10 cm from a convex lens of focal length 20 cm. Find the
position, nature and size of the image.
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Answer 1

Answer:

h= 4 cm

u = -10 cm

f = 20 cm.

According to lens formula,,

1/v - 1/u = 1/f

1/v = 1/f + 1/u

1/v = 1/20 - 1/10

1/v = -1/20

v = -20

We have, m = v/u

= -20/-10 = 2

Also, m= h'/h ( where h = height of object and h'= height of image)

2=h'/4

h' = 4X2 = 8cm.

Therefore, the image is real and inverted