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

The Correct Option is B

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.