A candle 5cm in size is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. the distance of the candle from the lens is 30cm (a) By calculation, determine the position and size of the image formed. (b) Also calculate the power of the lens. (c) How will the focal length of the above lens be affected on cutting it into two equal halves along the principal axis? What change can be observed in the formation of image in this case?
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ho=5cm
f=+20cm
u=-30cm
1/v-1/u=1/f
1/v=1/f+1/u
=1/20-1/30
=3-2/60
1/v=1/60
v=60cm
m=-v/u
=-60/-30
=60/30
m=2
if the lens is cut along the principal axis then there will be no change in the focal length of lens but it is cut perpendicular to principal axis then focal length will be twice the original one.
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