Thursday, 9 July 2009

Electromagnetic Radiation (a.k.a. Light)

Electromagnetic Radiation (a.k.a. Light):
The wavelength of the light determines its characteristics. For example, short
wavelengths are high energy gamma-rays and x-rays, long wavelengths are radio
waves. The whole range of wavelengths is called the electromagnetic spectrum.

Our eyes only see over the following range of wavelengths:

Wave Properties:
Due to its wave-like nature, light has three properties when encountering a
1) reflection
2) refraction
3) diffraction
When a light ray strikes a medium, such as oil or water, the ray is both refracted
and reflected as shown below:

The angle of refraction is greater for a denser medium and is also a function of
wavelength (i.e. blue light is more refracted compared to red and this is the origin
to rainbows from drops of water)

Diffraction is the constructive and destructive interference of two beams of light
that results in a wave-like pattern

Doppler effect:
The Doppler effect occurs when on object that is emitting light is in motion with
respect to the observer. The speed of light does not change, only the wavelength. If
the object is moving towards the observer the light is ``compressed'' or blueshifted.
If the object is moving away from the observer the light is ``expanded'' or

We can use the Doppler effect to measure the orbital velocity of planets and the
rotation of the planets.

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