# Light Bulb and Transmitted Intensity?

1. Oct 4, 2015

### AimlessWander

1. The problem statement, all variables and given/known data

You have a light bulb where the filament (in vacuum space) starts to glow. This light hits the glass of the bulb at 90 degrees from distance R and is transmitted through the glass of thickness s into the air, of index of refraction nair.

So light travels like this: vacuum -> glass (thickness s) -> air.

How do you find the intensity of light transmitted?
Answer should be in terms of the absorption coefficient α, nair, R, thickness s, and Iο. Index of refraction of a vacuum is 1.
2. Relevant equations
Beer Lambert's law?
Fresnel's Equations?

3. The attempt at a solution
I tried using Fresnel's equations but couldn't incorporate thickness s , R, and the absorption coefficient α.

2. Oct 5, 2015

### CWatters

Not my field at all (I've long since forgotten what Beer and Fresnel is all about) but since you haven't had had a reply...

Presumably the light emitted by the filament is spread out uniformly over the surface area of the sphere R. So the larger R the more spread out the light is and the lower the intensity ("amount of light per unit area").

Then it's attenuated by the absorption of the glass (proportional to thickness?)