an obejct is placed 60 cm in front of concave lense and its focal lenght 30 cm find it image distance......
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Answered by
2
Given,
u=30 cm
f=20 cm
v=?
Here,
1/u + 1/v = 1/f
1/30 + 1/v = 1/20
1/v = 1/20 - 1/30
1/v = 1/60 (use calculator )
v= 60 cm
( u, v, f are always in ‘+’ in concave.
But ‘-’ in convex)
Now,
(Since image is formed on the same side of the object , the image is real)
v-u = 60 - 30 = 30 cm
So the distance between object and image is 30 cm.
praanya:
this is wrong
Answered by
0
u = - 60 cm ( sign convention for concave lens)
f = -30 cm ( same reason)
1/f = 1/v - 1/u
1/f + 1/u = 1/v
1/v = 1/-30 + (1/-60)
1/v = 1/-30 -1/60
1/v = -2 -1/60. (L.C.M)
1/v = -3 / 60
v = 60/-3
v = -20 cm
Image distance = -20cm
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