Thursday, February 23, 2012
   
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Light

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Subject Index - Science

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1.  Light is the name for a range of electromagnetic radiation that can
be detected by the human eye. Because light has both electric and magnetic fields,
 it is also referred to as electromagnetic radiation.

2.  Light is a beam of energy that moves in a wave.

3.  A light wave consists of energy in the form of electric and magnetic fields.
The fields vibrate at right angles to the direction of movement of the wave,
and at right angles to each other.

4.  Light waves come in many sizes. The size of the wave,  the distance between
two wave peaks, is called a wavelength.

5.  The wavelengths of the light that most people can see ranges from 400 to 700 
billionths of a meter.

6.  The human eye needs light to see.

7.  Light travels very fast and in a straight line, until something bends it.
The straight waves of light are called light rays.

8.  Light travels at about 186,000 miles per second [300,000 kilometers per second],
Light from the sun takes about 8 minutes to go 93 million miles (149 million kilometers) 
to earth.  Really long distances can be measured in light years.  This would be the distance
that light can travel in a year, or 5,865,696,000,000 miles
(9,460,800,000,000 kilometers).

9.  Light is produced and controlled in many ways.  A lens helps to control light
that comes into the eye and into the lens of a camera.  Light is also used in copymachines,
televisions, satellites, telescopes, and medical system.

10.  Plants convert light energy from the sun into food.  This process is called photosynthesis.

purplelights800,000,000 kilometers).

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