RRB Group-D Model Paper 18 with answers for online practice

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 meter (m).

So the SI unit of power = 1/(SI unit of focal length) = ${\mathit{m}}^{-1}$ = Dioptre (D).

$1{\mathit{m}}^{-1}$ = 1 D

1. The Watt is the SI unit for 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. The centimeter measures the distance.
5. SI unit of distance is meter.