Microwaves, Infrared and Visible Light

Satellite Communication

Microwaves are used to send signals to satellites which can send the signals on to distant locations. The satellites orbit the Earth, thousands of kilometres above the surface. The returned signal is received by a satellite dish. 

Microwave Ovens

In microwave ovens, microwave radiation is emitted by the oven and then absorbed by water molecules in the food. This energy heats up the water molecules, which also heat up the surrounding molecules via heat transfer. 

Infrared waves are emitted when objects heat up. This means that detection of infrared waves can be used to detect warm objects and measure temperature from a distance. This can be used by an infrared camera to create an image where different colours represent different temperatures, such as the one shown on the right hand side. 

Objects also heat up when they absorb infrared radiation. Electric heaters and the heating element inside toasters both emit infrared radiation, along with a small amount of visible light, in order to heat up the air and your toast. 

Visible light is the range of wavelengths through which we see the world. However it can also be used for communications. 

Visible light is used in optical fibres made of glass to transmit information. The visible light travels along the fibre by reflecting off the inner surface of the fibre and is not refracted or transmitted through the fibre. This technology is now commonly used for internet connections.