A concave mirror of focal length 20cm is placed at a distance of 70cm from the wall. How far from the wall should an object be placed so that the image formed by the mirror falls on the wall?
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Explanation:
screen or image distance will be wall
that is 70 cm
now according to mirror formula
1/f = 1/v + 1/u
given focal lenght = -20cm
u = -70 cm
putting values
1/-20cm = 1/v + 1/-70cm
1/-20cm + 1/70 cm = 1/v
1/v = -5/140
v = 140÷5
v = -28cm
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