Question

an object is placed at a distance of 20.0 cm from a concave mirror of focal length of 15.0 cm . the screen is placed in front of the mirror to get a sharp image of the object . what is the distance of the screen from the mirror.
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Answer 1

20 cm is the distance of the screen from the mirror

Answer 2

Answer:

We have,

u= -20cm, f= 15cm, v= ?

Using mirror formula,

1/f=1/v+1/u

1/15=1/v-1/20

1/15+1/20=1/v

(4+3)/60=1/v

7/60=1/v

v=60/7 cm =8.5714 cm

Therefore the screen is placed a distance of 8.5714 cm from the mirror