Question

determination of the focal length of concave mirror convex lens by obtaining the image of a distant​
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Answer 1

use the mirror formula

1/v + 1/u = 1/f

where v is image distance

u is object distance

f is focal length

Answer 2

Fixing the concave lens and locating a distant object is the primary step either from a window or through a screen.

The screen must be placed behind the lens.

Adjusting the lens is important to view a sharp image that is diminished and inverted at the same time.

The distance of the optical centre and the screen must be calculated to find the focal length.