Question

An object is kept at a distance of 100cm for
lens of power-4D then the image distance
is


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Answer 1

$\large\underline{\blue{\sf \red{\bigstar}.}}$ Given :-

• An object is kept at a distance of 100cm for lens of power -4D.

$\large\underline{\blue{\sf \red{\bigstar}.}}$ To find :-

• Image distance ?

$\large\underline{\blue{\sf \red{\bigstar}.}}$Solution :-

• Object distance (u) = 100cm

• Power (P) = - 4 D

$\large\underline{\blue{\sf \red{\bigstar}.}}$As we know that

• → Power = It is the reciprocal of focal length

$\large\underline{\blue{\sf \red{\bigstar}.}}$According to question:-

• → P = 1/f

• → - 4 = 100/f

• → - 4f = 100

• → f = - 100/4

• → f = - 25 cm

$\large\underline{\blue{\sf \red{\bigstar}.}}$According to lens formula:-

• → 1/v - 1/u = 1/f

• → 1/v = 1/u + 1/f

• → 1/v = -1/100 + (-1)/25

• → 1/v = - 1/100 - 1/25

• → 1/v = -1 - 4/100

• → 1/v = -5/100

• → 1/v = -1/20

• → v = - 20cm

$\large\underline{\blue{\sf \red{\bigstar}✩ Hence:- }}$

$\large\underline{\pink{\sf \red{\bigstar} • Image \:\:distance \:\: is \:\:- 20cm}}$

Answer 2

Explanation:

i hope this is fine.........