Question

Determine the correct option.
The brightness producing power of a source
A) Does not depend on the power
B) Does not depend upon wavelength emitted
C) Depends on the power
D) None of these

Answer 1

We know that yellow colour is perceived more by a human eye when compared to other colours. It means that the perception of light by a human eye and colour of the source determines the brightness. Now as we know that the colour of light depends on its wavelength.

Complete step by step solution:
Brightness is the quality or state of giving out or reflecting light. We know that brightness depends upon how our eyes perceive light. Our eyes perceive yellow colour the most, yellow light tends to look brighter than reds or blues. Hence, we can say that brightness depends upon the colour of the source. Now we know the colour of visible light is related to its wavelength. Each colour has a different wavelength. Red has the longest wavelength, and violet has the shortest wavelength. So, brightness is also somewhat influenced by wavelength. Wavelength is the distance between two successive peaks.

Now as we know our eyes detect brightness by the number of photons entering our retinas. The energy of the photon depends on its frequency. The higher the frequency, the more energy the photon has. And the number of photons depends upon the power of the source, that’s why brightness producing power also depends on the power of the source too.

Therefore, option B and option C both are correct.

Note: We have to remember that brightness is the subjective visual sensation related to the intensity of light coming out from a surface or a point source. In other words, brightness is the perception extracted by the luminance of a visual target. Different wavelengths generate different coloured lights. And similarly, different lights have different brightness.