Question

Describe how you would observe the light coming from a light bulb. What is the color, directionality, intensity, etc.?

Answer 1

A light bulb, is usually a Tungsten wire bulb, where the filament is made of tungsten, which is packed in an inert gas chamber(to prevent the tungsten from being oxidised in the very high temperatures in the presence of other impurities) and when electric current passes through it, it emits radiation in all possible directions, in a vary large bandwidth of wavelength/ frequencies.

A bulb can be considered as a point source and the intensity of the light is inversely dependent on the square of the distance. We perceive the color to be yellow, but actually, it emits in the entire visible spectrum and in the IR region too(as heat) (it is essentially white light, with more intensity, concentrated around the yellow region, but the way we consider white light is with the color "white". But essentially, white light means light with all the possible wavelengths, and bulb gives out more white light than an LED/CFL lamp).

Unlike Lasers, bulb light doesnt have a specific directionality and is incoherent source of light. Here, the mechanism of emission is spontaneous emission.