Question

An optical bench in the laboratory has a scale of 100 cm marked on it. A spherical lens is placed at 65cm of the optical bench. The image of a distant tree is formed on screen placed at 50cm of the optical bench. Hence find out (a) the focal length of the lens (b) also write the nature of the image formed .

Answer 1

1)focal length = 15cm from lens

Or image will form at focus

2) image will be virtual ,erect and highly diminished

Answer 2

Welcome dear,

● Answer -
1) Focal length = 15 cm
2) Nature of the image = real, inverted and minimized.

● Solution -
Lens is placed at 65 cm of optical bench and image is formed at 50 cm of optical bench.

Here,
u = distant = ∞
v = 65-50 = 15 cm

Using lens formula,
1/f = 1/v - 1/u
1/f = 1/15 - 1/∞
1/f = 1/15
f = 15 cm

Nature of the image formed is real, inverted and minimized.

Hope this helps you...