3. An object of 7cm high
is placed at 27cm in front
of a concave mirror of
focal length 18cm, At
what distance from the
mirror should a screen be
placed so that a sharp
focussed image can be
obtained. Calculate the
size and nature of the
image.
Answers
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Explanation:
Given that
u = – 27 cm
f = – 18 cm
h0 = 7.0 cm
Find out
We need to find out size and nature of image
Formula
We know the mirror formula that
1/v = 1/f- 1/u
1/v = -1/18 + 1/27 = -1/54
V = – 54 cm
The screen must be placed at a distance of 54 cm from the mirror in front of it.
hi/h0= v/u
hi/h0= v/u
hi/7 = +54/-27 hi= -2 x 7 = -14 cm.
Thus, the image is of 14 cm length and is inverted image
Given that
u = – 27 cm
f = – 18 cm
h0 = 7.0 cm
Find out
We need to find out size and nature of image
Formula
We know the mirror formula that
1/v = 1/f- 1/u
1/v = -1/18 + 1/27 = -1/54
V = – 54 cm
The screen must be placed at a distance of 54 cm from the mirror in front of it.
h1/h0= v/u
h1/h0= v/u
h1/7 = +54/-27 hi= -2 x 7 = -14 cm.
Thus, the image is of 14 cm length and is inverted image