SI unit of intensity of light is:

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Newton

Kelvin

Kilogram

Candela

answer is D.

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Detailed Solution

Concept- We will first examine the definition of light intensity in this query. Both electric and magnetic fields are present in light. These amounts all have energy. As a result, we will calculate the light's intensity using the wave's energy idea and then obtain the SI unit for light intensity.
Let

be the pointing vector then the magnitude of the pointing vector gives the power per unit area of the wave.

Where are the current values at the observation point, and?
The fact that

Where,

is speed of light
We can also write:

The Pointing vector

fluctuates very rapidly with time. The frequency is about

.
Intensity of light:-
It is defined as the time average of magnitude of pointing vector '

The average value of

function is

. We thus obtain:

The intensity of light may also be expressed in terms of rms magnitude of the fields. With

, we obtain