# Quiz Question

One of a continuing series

This one will be trivial to most. Puzzling to some.

So, I have this special glass. See the illustration above. Disregard the colors. I put those in for interest. Color doesn’t have anything to do with the Quiz Question.

Light enters the pane of glass from the right. Only half of it emerges from the other side. Due to the index of refraction of the glass and the surrounding medium being the same, there is no surface reflection. Half of the light entering the pane is absorbed, and only half comes out the other side.

If I double the thickness of the pane, how much light comes out the other side? Post your answer in the comments section below.

## 3 thoughts on “Quiz Question”

1. If one pane produces a one stop reduction in light, then two panes will produce a two stop reduction. Meaning 25% of the light will make it through.

2. Pingback: Quiz Question | Skeptical Analysis

3. Gregory H. Aicklen says:

Addressing your question on Facebook, as to what exponential absorption says about the process of absorption: absorption is statistical in nature. The glass filter is “doped” with molecules that have electrons with resonant frequencies falling in the range of the light that’s to be filtered. Photons that pass into the filter have a probability, dependent on the level of doping, to collide with doped molecules and be absorbed (i.e. converted to vibration and thus heat energy).

The glass in your example does not absorb 50 units of the light that enters, it absorbs 50% of the light that enters. Doubling the thickness is like running the light through two 50% filters: the first filter takes 50%, the next filter takes 50% of that 50%, leading to 25% of the light passing through unhampered.

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