Question

A needle placed 45cm from a lens forms an image on a screen placed 90cm on the other side of the lens. Identify the type of the lens and determine its focal length. What is the size of the image if the size of the needle is 15.0cm?​

Answer 1

U= 45

V= 90

Science the image is virtual therefore, it must be a convex lense

1/f = 1/v -1/u

1/f = (1/90) - ( -1/45)

f = 30cm

m = v/u = (90/-45) = -2

m = hi/ho

-2 = hi/5

hi = -10cm