. A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed.
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A concave lens always form a virtual,erect image on the same side of the object
v = -15 cm
f = -20 cm
u = ?
since 1/u + 1/v = 1/f
1/u = 1/v -1/f
1/u = 1/-15 - 1/-20
= -1/15 + 1/20
= -4/60 + 3/60
= -1/60
1/u = -1/60
u = -60
object size = 5
m= v/u
m= -15/60
= 1/4
image size = 5×1/4
5/4 cm
hope it help u☺☺☺☺☺
v = -15 cm
f = -20 cm
u = ?
since 1/u + 1/v = 1/f
1/u = 1/v -1/f
1/u = 1/-15 - 1/-20
= -1/15 + 1/20
= -4/60 + 3/60
= -1/60
1/u = -1/60
u = -60
object size = 5
m= v/u
m= -15/60
= 1/4
image size = 5×1/4
5/4 cm
hope it help u☺☺☺☺☺
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