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عبدالله المالكي الإثنين أبريل 06, 2009 10:56 pmThe entire electromagnetic spectrum is made up of ultraviolet, visible light, and infrared. The human eye can only see the light sector of the spectrum. The ultraviolet and infrared are wave energy that can not be seen by our eyes. William Herschel began down the road to discovering the electromagnetic spectrum in 1799. He wanted to find out how light and heat were connected. He used a prism to break up white light and used a thermometer to measure the temperature of each of the different colors. Each color, he found, did not have the same temperature. Red had the highest reading of all of the colors, while violet gave the lowest.
However, past the red that we are able to see, Herschel found something that was even hotter than red itself. This end of the electromagnetic spectrum he called infrared. Infrared can be felt, but it can not be seen by the naked eye. The wavelengths of the visible spectrum are all medium in length. The wavelengths of infrared light are very slow. Everything emits infrared light. Even things found in your freezer emit it. Infrared can be found in anything above absolute zero. The amount of infrared light that an object emits depends on its temperature. A human gives off much more infrared light than an ice cube would. No matter what time of day it is, the same amount of infrared light is given off. Because of this, movement can be detected in the dark with infrared detectors. Some animals, like snakes of the pit viper family, are able to pick up on infrared waves to detect their prey. To the left is an infrared picture of the comet Iras-Araki-Alcock. It was taken by the Infrared Astronomical Satellite. By looking at the different colors, we can tell where the warmest areas of the comet are. The red and yellow areas are the nucleus of the comet, the warmest areas, while its blue tail is cooler.
Infrared Processing and Analysis Center,
Caltech/JPL. IPAC is NASA's Infrared
Astrophysics Data Center.
At the other end of the spectrum, past violet, is ultraviolet. Ultraviolet was discovered by Wilhelm Ritter in 1801. He dipped strips of paper into silver nitrate and shown certain types of light on them. Silver nitrate goes under a chemical reaction when exposed to light, and Ritter found that the reaction was different depending on the type of color that was shined on it. When exposed to violet light, the paper would turn much darker than any of the other colors. Knowing that Herschel had found unseen light at the red end of the spectrum, Ritter decided to see if there was at the violet end. When he did this, the paper turned darker than when exposed to violet light, proving that there was light beyond violet. This invisible light was named ultraviolet. Ultra violet light is often given off by the sun. Most are reflected by the ozone layer, but some do get into our atmosphere. These rays damage unprotected skin and have been known to cause skin cancer
However, past the red that we are able to see, Herschel found something that was even hotter than red itself. This end of the electromagnetic spectrum he called infrared. Infrared can be felt, but it can not be seen by the naked eye. The wavelengths of the visible spectrum are all medium in length. The wavelengths of infrared light are very slow. Everything emits infrared light. Even things found in your freezer emit it. Infrared can be found in anything above absolute zero. The amount of infrared light that an object emits depends on its temperature. A human gives off much more infrared light than an ice cube would. No matter what time of day it is, the same amount of infrared light is given off. Because of this, movement can be detected in the dark with infrared detectors. Some animals, like snakes of the pit viper family, are able to pick up on infrared waves to detect their prey. To the left is an infrared picture of the comet Iras-Araki-Alcock. It was taken by the Infrared Astronomical Satellite. By looking at the different colors, we can tell where the warmest areas of the comet are. The red and yellow areas are the nucleus of the comet, the warmest areas, while its blue tail is cooler.
Infrared Processing and Analysis Center,
Caltech/JPL. IPAC is NASA's Infrared
Astrophysics Data Center.
At the other end of the spectrum, past violet, is ultraviolet. Ultraviolet was discovered by Wilhelm Ritter in 1801. He dipped strips of paper into silver nitrate and shown certain types of light on them. Silver nitrate goes under a chemical reaction when exposed to light, and Ritter found that the reaction was different depending on the type of color that was shined on it. When exposed to violet light, the paper would turn much darker than any of the other colors. Knowing that Herschel had found unseen light at the red end of the spectrum, Ritter decided to see if there was at the violet end. When he did this, the paper turned darker than when exposed to violet light, proving that there was light beyond violet. This invisible light was named ultraviolet. Ultra violet light is often given off by the sun. Most are reflected by the ozone layer, but some do get into our atmosphere. These rays damage unprotected skin and have been known to cause skin cancer
