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 :

A biconvex lens has a radius of curvature of magnitude 20 cm. Which one of the following option best describe the image formed of an object of height 2 cm placed 30 cm from the lens?

A converging beam of rays is incident on a diverging lens. Having passed through the lens the rays intersect at a point 15 cm from the lens on the opposite side. If the lens is removed the point where the rays meet will move 5 cm closer to the lens. The focal length of the lens is

A lens having focal length f and aperture of diameter d forms an image of intensity I.

Apreture of diameter   in central region of lens is covered by a black paper. Focal length of lens and intensity of image now will be respectively:

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?

When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts as a plane sheet of glass. This implies that the liquid must have refractive index:

If a convex lens having focal length f and refractive index 1.5 is immersed in water then new focal length will be