Purcell's Black Body Box

black body - quantization - radiation

What it shows:
A black body box is an idealized black body radiator. That is, any light emerging from the interior of the box is purely a product of the box’s temperature.

How it works:
As the light emerging from the cavity should be a product of the temperature of the cavity, a cardboard box at room temperature should look black inside (emitting in the infra-red). To prove the point, Purcell’s box is painted white inside. A hole 6cm × 6cm is cut into the center of the lid, and to aid contrast, an area 25cm × 30cm surrounding the hole is covered in black felt.Looking in through the hole, the box appears black inside. Removing the lid will reveal the bright white interior.

Comments:
Any box will do, provided it has a nice slip-on lid. Named after Prof. E. Purcell who’s idea it was, and what a great idea it is. Very useful illustration of the mysterious Black Body. Rating ***