Question

How do you find the focal length of conacave mirror in the lab​

Answer 1

Answer:

by using formula of 1/f=1/v+1/u

Answer 2

Explaination

Refer to the attachment

When the lines are passed from focus they reflect back to form parallel lines. But it is a convention that parallel lines meet at infinity.

Thus, the image is formed in infinity.

The image obtained will be highly magnified, Real and inverted.

So, we will not clearly see the image in the mirror as the image formed is highly magnified

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Formula for focal length

1/f = 1/v + 1/u

where, f = focal length

v = image distance

u = object distance