Experiment of December 8, 2016:

The time to submit an answer is over. You can now view the solution of the experiment.

Solution video:

For technical reasons you need to click twice to first load the video and then start playing it.

Experiment:

Question:

How does the appearance of the grease spot change?

A) Near the lamp at the front, the spot appears dark: near the lamp at the back, it appears bright. Precisely half way between the lamps, the spot disappears.

B) Near the lamp at the front, the spot appears bright: near the lamp at the back, it appears dark. Precisely half way between the lamps, the spot disappears.

C) Near the lamp at the front and the lamp at the back, the spot appears dark. Precisely half way between the lamps, the spot is brightest.

D) Near the lamp at the front and the lamp at the back, the spot appears bright. Precisely half way between the lamps, the spot is darkest.

Advice of the day:

Mr. Santa places himself behind one candle in line with both candles. One candle is hence nearby, the other one further away. Inbetween is the sheet of paper which he moves towards of away from him.