An image by a concave mirror is 4 timed greater than the object of the radius of curvature is 20 cm, determine the object distance if front of the mirror.
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Answered by
4
h' = image size
h = object size
h' = 4h
Now,
m = h' / h
m = 1/4
Also,
m = - v/u
1/4 = -v / u
u = -4v ....(1)
Radius of curvature = 20 cm
So, focal length = 20/2 = 10 cm
We know,
1/f = 1/v + 1/u
1/10 = 1/v - 1/4v
1/10 = 4 - 1/4v
1/10 = 3/4v
4v = 30
v = 30/4
v = 15/2
v = 7.5 cm
Substituting value of v in (1)
u = -4v
u = -4×15/2
u = -2 × 15
u = -30 cm
Hence, Object distance is 30 cm infront of the mirror.
Answered by
2
Answer:
Object distance =30 cm
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