physics 1 (new version)

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Infared radiation

 Every objective emits (gives out)  and absorbs ( takes in) infared radiation. The hotter an object is, the more infared radiation it emits in a given time. Infared radiation travels in waves.

Radiation can even pass through the vacuum of space. This is why we can still feel the heat of the Sun, although it is 150 million km away from the Earth.

dark, dull surfaces are better at emitting and absorbing infared radiation than a light, shiny surface. The colours of rainbows are known as the visible light.

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The Electromagnetic Spectrum

radio, microwaves, infared radiation, visible light, ultra-violet, x-rays and gamma rays are all part of the electromagnetic spectrum. Electromagnetic waves are electric and magnetic waves that travel through space.

how to remember the above: Rich Man In Very Unusual X-rated G-strings.

The Radio end of the spectrum has the longest wavelength and the lowest frequency but the Gamma end of the spectrum has the shortest wavelenght and the highest frequency.

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Energy from the sun

The sun emits all types of electromagnetic radiation. The earths atmosphere blocks most of the radiation that would harm us but it doesnt block infrared radiation.

A solar furnace uses a giant reflector that focuses sunlight.

The temperature at the focus of the solar furnace can reach thousands of degrees. (the temperature of the sun is 5500 degrees celcius)

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The greenhouse effect

The earths 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 objectsis trapped inside by the glass because the objects emit infrared radiations of longer wavelengths that cant pass through the glass. (the greenhouse stays warm)


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The greenhouse effect 2

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.

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'.

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Surfaces and radiation

A light, shiny outer surface emits much less radiation than a dark and dulll surface.

When you use a photocopier infrared radiation from a lamp dries the ink otherwise it would smudge. black ink absorbs more infrared radiation than the white paper.


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