Question

Q5:

a. Whenever you look at an element undergoing fluorescence, why do you see multiple colors in a line spectrum, but only a single color with your un-aided eyes?

b. Based on what you can through spectroscopes, how does the light from the three light sources (LED bulb, a fluorescent tube bulb, and an “old fashioned” incandescent bulb) compare to each other ?

Answer 1

Answer (a) The fluorescence spectrum is a broad-band spectrum. The un-aided eye is not able to resolve the constituent wavelengths in the broad-band spectrum and hence a single color is visible. However, in the line spectrum, all the constituent wavelengths are well resolved and we can see them separately.

Answer (b) When we look through the spectroscope at an “old fashioned” incandescent bulb, we find that the incandescent light gives a full continuous spectrum. A LED bulb matches incandescent to a marginal degree and does not produce a full spectrum, like an incandescent light bulb does. The fluorescent tube bulb emits distinct lines characteristic of the phosphor and mercury spectrum.