JEE Physics 2024 Question with Solution

Given: The candela is defined using monochromatic radiation of frequency $A \times 10^{12} \, \text{hertz}$ and radiant intensity $\frac{1}{B}$ watt per steradian.

Find: The values of $A$ and $B$.

From the SI definition, candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency

and that has a radiant intensity in that direction of

Comparing with the given form:

and

we get

and

Given: A question based on the SI base unit candela.

Find: Which option matches the standard definition.

The standard definition states that candela corresponds to monochromatic radiation of frequency $540 \times 10^{12} \, \text{hertz}$.

It also states that the radiant intensity in that direction is $\frac{1}{683} \, \text{watt per steradian}$.

Therefore, the required pair is $540$ and $683$. The correct option is B.