Question

The power of lens is 4D, An object is kept at a distance of 100 cm from this lens.
Calculate the- (i) image distance (ii) magnification
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Answer 1

Answer:

u= -100 cm (according to sign convention )

p= -4 (as power is negative so the lens is concave lens, and that's why we took u negative )

p =100/f (because u is given in cm so we use 100/f)

-4=100/f

f= -25 cm

by lens formula

1/f=1/v-1/u

-1/25=1/v -(-1/100)

1/v= -1/25-1/100

1/v= -4-1/100

1/v= -5/100

v= -20 cm

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