Question

A concave lens of 20cm focal length forms an image of 15cm from the lens. compute the object distance

Answer 1

⭐ Hello Mate⭐
✔️Here is your answer ✔️
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Here,
Focal length= -20(as it is concave lens)
v= -15 (as concave lens always forms virtual and erect image on left of lens)
u= ? (to be calculated)

Putting these values in lens formula,
1/ -20 - 1/u = 1/ -15
-1/ u= 1/-15 + 1/20
-1/u = -4+3/60
-1/u = -1/60
-u = -60
[u =60]

✌️Hope it helps you ✌️
Thank you

Answer 2

1/-20=1/-15 -1/u

1/u=-1/15+1/20

1/u=-1/60

u=-60cm

```I hope it will help you```