A biconvex thick lens is constructed with glass (μ = 1.50). Each of the surfaces has a radius of 10 cm and the thickness at the middle is 5 cm. Locate the image of an object placed far away from the lens.


Biconvex lens with each surface has a radius (

Thickness of lens (t) = 5 cm

Refractive index of lens ==1.50

Position of object =

At first refraction occurs at A

By using lens equation:

Now, the second refraction occurs at B

Object distance =u= (30-5) = 25 cm (a virtual object)


So, (by using lens equation)

So, the image is formed 9.1 cm further from the 2nd surface of the lens.