Question

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency $'A' \times 10^{12} \, \text{hertz}$ and that has a radiant intensity in that direction of $\frac{1}{'B'} \, \text{watt per steradian}$. 'A' and 'B' are respectively:

• A. 540 and $\frac{1}{683}$
• B. 540 and 683
• C. 450 and $\frac{1}{683}$
• D. 450 and 683

Answer 1

Answer: (B)

540 and 683

Answer 2

The definition of candela specifies:
- $A = 540 \times 10^{12}$ hertz is the frequency of the monochromatic light.
- $B = 683$ is the luminous efficacy in terms of watts per steradian.
These values are based on the standard SI definition of candela.