Question

The SI unit of power of lens is:
1. Hertz
2. Lumen
3. Ohm
4. Dioptre

Answer 1

Correct Answer - Option 4 : Dioptre

The correct answer is Dioptre.

CONCEPT:

• Power is the ability to bend light and it is equal to the reciprocal of the focal length of the lens/mirror in meters.

Power (P) = 1/f

Where f is the focal length of the lens/mirror.

EXPLANATION:

• The SI unit of the focal length is the meter (m).

So the SI unit of power = 1/(SI unit of focal length) = m^-1 = Dioptre (D)

1 m^-1 = 1 D

1. Watt is the SI unit of power for energy consumption.
2. The SI unit of the power of a lens is given by Dioptre. 
3. Candela is the SI unit for the luminous intensity of an object.
4. Centimeter measures the distance. 
5. SI unit of distance is metre.