Question

Image is obtained on a screen by keeping an object at 25 cm and then at 40 cm in front of a concave mirror. Image in the
former case is four times bigger than in the latter. Then the focal length of the mirror must be :
correct answer is f = 20
Need explanation

Answer 1

Answer:

4m2 = f-40cm------(i)

m2=f-25cm-------(ii)

Dividing (i) / (ii)

4f-100=f-40

3f=60

f=20cm

Hope it helped

Answer 2

Answer:

20 cm

Explanation:

hopes it helps you