MY PBL PROJECT

Introduction

How does the radiometer work?

The radiometer is made of a glass bulb from which most of the air is removed, therefore it creates a partial vacuum and a rotor that is mounted on a vertical support inside the glass bulb. The vanes are polished or white on one side, black on the other. When exposed to light, or infrared radiation, the vanes turn with no apparent motive power, the dark sides retreating from the radiation source and the light sides advancing. Cooling the radiometer causes rotation in the opposite direction.

The radiometer was invented in 1873 by a chemist named Sir William Crookes.

Materials

• • Radiometer-

• Hair dryer-

Procedures

1- Place the radiometer in a room full of light.

2- Observe how the vanes rotate.

3- Place the radiometer under a fluorescent lamp in the room. Turn off the overhead lights in the classroom. Observe rotation of vanes and make some observations about the speed of the vanes.

4- Point a laser or a xenon flashlight towards the radiometer, observe the vanes rotation speed.

5- Blow the radiometer with a hair dryer, observe how the vanes react with heat.