Question

a concave mirror produces three times enlarged image of an object placed at 10cm in front of it what is the radius of curvature of the mirror

Answer 1

u= -10 cm
m= +3 = -v/u
=) v= 30 cm
1/f=1/v+1/u
=)1/f=u+v/uv
=)1/f= -10+30/-300
       =20/-300
=)f= -15cm
R=2f= -30cm.

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Answer 2

u = -10cm
m = 3
 therefore v= 30 cm
1/f = 1/v +1/u
      = 1/30-1/10
 On solving we get f = -15cm
But we need to find the value of R
hence we have the relation 
R=2f
  = 2 x -15
  = -30cm
Therefore the radius of curvature of the concave mirror is -30 cm

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