Question
Tue December 25, 2012 By: Rajarshi Basu

Q1.An object is kept in front of a concave mirror of focal length 15cm.The image formed is 3 times the size of the object.Calculate two possible distances of the object from the mirror

Expert Reply
Tue December 25, 2012
f=-15cm
h1=3h0
for real image
m
  m =-3
v=3u
using
(-1/15) = 1/u + 1/(3u)
 
u=-20cm
for virtual image,
m
 m =+3
so, v=-3u
(-1/15) = 1/u  + (-1/3u)
u= -10cm
The two possible positions are 10 cm and 20 cm in front of concave mirror.

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