H.1(1) – Crooke’s Radiometer
This apparatus shows the greater absorption of radiation by a black surface than by a reflecting white surface. The bulb is 99% evacuated. It has four vertical plates connected to freely movable shaft (around vertical axis). Each vane has one side white and the other black. When brought close to a light source, the black side absorbs heat. As the atoms of gas left in the blub collide with them, they pick up energy and make the plates turn around the axis.
There are four radiometers available, of 7 cm diameter and 12 cm high.
H.1(2) – Concave Mirrors
Concave mirror has a 68 cm focal length and can be used to reflect heat radiation.
H.1(3) – Solar Furnace
Solar furnaces are used as high-temperature furnaces for experimental or laboratory research in heating of liquids or metals. This solar furnace consists of a concave mirror (12 inch diameter), a small copper container (1.25 inch base diameter) is the place of the focal point. The mirror and the cup can be rotated for fine adjustment to direct the reflected sun light rays at the cup. Using a digital thermometer one can monitor the temperature changes of the water inside the cup. The thermometer change is dramatic and one can see the water boiling in less than 3 minutes.
Caution: The Solar Furnace generates extreme heat and may be dangerous if not used properly. When the furnace is not in use, keep the mirror away from the sun. While the furnace is in use , keep the sun’s rays focused on the receiver and avoid placing your hands in front of the mirror.
