The yellow colour has a greater luminous efficiency as compared to the other colours. Can we increase the illuminating power of a white light source by putting a yellow plastic paper around this source?
The illuminating power of the source cannot be increased by wrapping a yellow plastic around it.
The wide range of visible radiation is radiated by white light source. The yellow plastic blocks all the wavelength and emits only yellow wavelength of the light. This implies that a small fraction of the power emitted by the white beam of light.
Thus, the illuminating power of the source decreases when it is wrapped with yellow plastic.