Question

The brightness-producing capacity of a source
(a) does not depend on its power
(b) does not depend on the wavelength emitted
(c) depends on its power
(d) depends on the wavelength emitted.

Answer 1

The brightness-producing capacity of a source (c) depends on its power and (d) depends on the wavelength emitted.

Explanation:

• Yellow colour is perceived more by a human eye when compared to other colours.
• This shows that the perception of light by a human eye and colour of the source determines the brightness.  
• In addition, wavelength of a light also determines the brightness.  Also, the power of source amounts to the number of photons entering into a human eye.  
• Hence, the power of source also determines the brightness.