Lens Maker's Formula - Practice Questions & MCQ

A thin convex lens made from crown glass has a focal length of f. When it is measured in two different liquids having refractive indices and  it has the focal lengths   respectively. The correct relation between the focal lengths is :

A convex lens, of focal length 30 cm, a concave lens of focal length 120 cm, and a plane mirror are arranged as shown.  For an object kept at a distance of 60 cm from the convex lens, the final image, formed by the combination, is a real image, at a distance of :

To find the focal length of a convex mirror, a student records the following data :

The focal length of the convex lens is ₁ and that of mirror is ₂. Then taking index correction to be negligibly small,  ₁ and ₂ are close to :

Diameter of a plano - convex lens is 6 cm and thickness at the centre is 3 mm. If speed of the light in material of lens is 2 x 10⁸ m/s, the focal length of the lens is :

An object 2.4 m in front of a lens forms a sharp image on a film 12 cm behind the lens. A glass plate 1cm  thick, of refractive index 1.50 is interposed between lens and film with its plane faces parallel to film. At what distance (from lens) should object be shifted to be in sharp focus on film?

A double convex thin lens made out of glass (refractive index, ) has both radii of curvature of magnitude . Incident light rays parallel to the axis of the lens will converge at a distance such that:

The focal length of the lens of refractive index  in air is . If air is replaced by water of , its focal length is: