Gold foil in transmitted light

Experiment no.: 9.10.4
Goldfolie im Durchlicht
White light that is reflected on a thin gold foil (about 22 nm) is golden. If it is transmitted through the gold foil, it is bluish. If the reflected and transmitted light are superimposed, white light is obtained again.

Images for this experiment

Experiment
Set-up
Projection separated
Projection superimposed