An object of height 1.2m is placed before a concave mirror of focal length 20cm so that a real image is formed at a distance of 60cm from it. Find the position of an object. What will be the height of the image formed?
Answers
Answered by
4
Given,
ho = 1.2m =120cm
f = - 20cm (since concave mirror)
v = - 60cm (since real images are formed in lhs of mirror)
Now,
1/f = 1/v + 1/u
1/-20 = 1/ - 60 + 1/u
1/u = - 1/20 + 1/60
1/u = - 2/60
u = - 30 cm. (position of the object)
now hi :-
hi/ho = -v/u
hi = - (-60 × 120) ÷ -30 = - 240 m = 2.4 cm
ho = 1.2m =120cm
f = - 20cm (since concave mirror)
v = - 60cm (since real images are formed in lhs of mirror)
Now,
1/f = 1/v + 1/u
1/-20 = 1/ - 60 + 1/u
1/u = - 1/20 + 1/60
1/u = - 2/60
u = - 30 cm. (position of the object)
now hi :-
hi/ho = -v/u
hi = - (-60 × 120) ÷ -30 = - 240 m = 2.4 cm
Answered by
2
Answer:
u = 30 cm
Explanation:
We have given :
Focal length = 20 cm
Image distance = 60 cm
We have to find object distance .
We know :
1 / f = 1 / v + 1 / u
Since image formed is real :
f = - 20 cm and v = - 60 cm
1 / u = 1 - 3 / 60
u = - 30 cm
Hence object distance is 30 cm .
Also given object height = 1.2 cm
We know :
h_i / h_o = - v / u
h_i / 1.2 = - 60 / 20
h_i = - 2.4 cm
Hence image height is 2.4 cm .
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