Question

An object of size 7.0um is placed at 27 in
front of concave mirror of focal length 18cm. At
what distance from the mirror should be placed.So that
a sharp focussed image can be obtained?
Find the size and nature of image.
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Answer 1

Answer:

when the object is placed at the infinity then the image is formed by the concave mirror is sharo and focussed

h=7cm

u=-28

f=-18

v=?.

by using mirror

l/f = 1/v + 1/u

1/v = 1/f - 1/u

1/v = 1/-18 - 1/-27

1/v = -1/18 + 1/27

1/v = -21 + 18/480

1/v = -3/480

1/v = -1/160

v = -160cm

The image is formed real and inverted

and the size of the image is -160cm