Question

The power of a lens is -5 dioptre.
(1)Find its focal length
(2)Name the type of lens.

Answer 1

Focal length=1/P

f=1/-5

f=-0.02m

Therefore the given lens is concave lens

Hope it helps y

Answer 2

Power of a lens. If a lens has a shorter focal length it is said to be more powerful. The power of a lens is defined as the reciprocal of the focal length. Lens power is measured in dioptres (D).

To measure the focal length of a converging (convex) lens. To measure the focal length of a converging (convex) lens. Using the formula: 1/u + 1/v = 1/f, the focal length f of the lens can be found.

There are two main types of lenses, known as convex (or converging) and concave (or diverging).