An object placed 45 cm from a lens forms an image on a screen place 90 cm on the other side of the lens. Identify the type of the lens and find its focal length.

Question

Philoid · Accepted Answer

According to the question;

Object distance, u= -45cm;

Image distance, v= 90 cm;

Focal length, f=?

By lens formula;

⇒ f = 30cm.

Since the focal length is positive, therefore the lens is convex lens of focal length 30cm.