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:
This query concerns the definition of the candela, a base unit within the International System of Units (SI). The candela quantifies luminous intensity in a specific direction from a source emitting monochromatic radiation.
The provided details are:
The frequency of the monochromatic radiation is \( A \times 10^{12} \, \text{hertz} \).
The radiant intensity in the specified direction is \( \frac{1}{B} \, \text{watt per steradian} \).
The problem presents choices for A and B. To determine the correct answer, one must refer to the established definition:
The candela is defined by a radiation frequency of 540 × 1012 hertz and a radiant intensity of 1/683 watt per steradian.
Consequently, the correct values for A and B from the given options are:
Frequency: 540 (corresponding to 540 × 1012 hertz)
Radiant Intensity: 683 (with the radiant intensity defined as \( \frac{1}{683} \, \text{watt per steradian} \))
Therefore, the correct option is 540 and 683.
The incorrect options are excluded because:
Frequencies of 450 do not align with the standard frequency used in defining a candela.
An option where B equals \( \frac{1}{683} \) is incorrect as it does not represent the required radiant intensity for a standard candela.
Thus, the accurate answer is 540 and 683, based on the SI definition of the candela.
