Done by:

Chua Wei Hern (9)

2O1

0A rainbow is 0an optical and meteorological phenomenon that

causes a spectrum of light to appear in the sky when the Sun shines on to droplets of moisture in the Earth's atmosphere.

0 It takes the form of a multicoloured arc.

What causes rainbows?

0 When there are water droplets in the atmosphere, during or immediately following a shower of rain, there will be thousands of these tiny droplets floating around in the air.

0 When light from the Sun encounters a water droplet that is spherical in shape, it penetrates the outer boundary of the droplet. As it enters, the light is refracted and dispersed into a continuous band of colors.

0 These colors are then reflected from off the back of the drop again as they pass through the front of the drop once more, thus being refracted still some more. These continuous band of colors as explained above, is due to the fact that the angle of bending is different for different wavelengths of light.

0 This explains the reason for the appearance of the band of colors which is due to their wavelength.

Light Dispersion0Light dispersion is the phenomenon in which the phase

velocity of a wave depends on its frequency, or when the group velocity depends on the frequency.

0Dispersion is sometimes called chromatic dispersion to emphasize its wavelength-dependent nature, or group-velocity dispersion (GVD) to emphasize the role of the group velocity.

0The most common example of light dispersion is probably a rainbow, in which dispersion causes the spatial separation of a white light into components of different wavelengths. 

Sources

0http://en.wikipedia.org/wiki/Rainbow0http://en.wikipedia.org/wiki/Dispersion_(optics)0Google images0http://science.howstuffworks.com/nature/climate-

weather/atmospheric/question41.htm