Infrared Radiation

Infrared radiation is energy transfer by electromagnetic waves.

All objects emit infrared radiation. 

The hotter an object is, the more infrared radiation it emits in a given time. 

You can use a thermometer with a blackened bulb to detect infrared. 

Radio waves, microwaves, infrared radiation and visible light are parts of the electromagnetic spectrum. So too are ultraviolet rays and X-rays. Electromagnetic waves are electric and magnetic waves that travel through space. 

Energy from the Sun

The sun emits all types of electromagnetic radiation. Fortunately for us, the Earth's atmosphere blocks most of the radiation that would harm us. But it doesn't block infrared radiation from the sun. 

The Greenhouse Effect

The Earth's atmosphere acts like a greenhouse made of glass. In a greenhouse: 

- short wavelength infrared radiation (and light) from the Sun can pass through the glass to warm the objects inside the greenhouse

- infrared radiation from these warm objects is trapped insie by the glass because the objects emit infrared radiation of longer wavelengths that can't pass through the glass

So the greenhouse stays warm. 

Gases in the atmosphere, such as water vapour, methane and carbon dioxide, trap infrared radiation from the Earth. This makes the Earth warmer than it would be if it had no atmosphere. But the Earth is becoming too warm. If the polar ice caps melt, it will cause sea levels to rise. Reducing our use of fossil fuels will help to reduce the production of 'greenhouse gases'. 

Dark, matt surfaces emit more infrared radiation than light, shiny surfaces.

Dark, matt surfaces absorb more infrared radiation than light, shiny surfaces.

Light, shiny surfaces reflect more infrared radiation than dark matt surfaces. 

Did you know...?

Scientists are developing blacker and blacker materials. These new materials have very tiny pits in the surface to absorb almost all the light that hits them. They can be used to coat the insides of telescopes so that there are no reflections.