LIGHT AND THE ELECTROMAGNETIC SPECTRUM
ODER OF ELECTROMAGNETIC SPECTRUM FROM LONGEST WAVES TO SHORTEST
Radio waves ------LEAST HARMFUL…..LONGEST WAVELENGTH
Visible light rays
Ultraviolet light rays
Gamma rays ------MOST HARMFUL…..SHORTEST WAVELENGTH
COLORS OF VISIBLE LIGHT
R O Y G B I V
Red, Orange, Yellow, Blue, Indigo, Violet
NATURE OF AN ELECTROMAGNETIC WAVE
An electromagnetic wave consists of an electric field and a magnetic field positioned at right angles to each other and to the direction of the motion of the wave.
Atoms are the building bocks of matter. An atom consists of a central core or nucleus surrounded by tiny particles called electrons.
Electrons are charged particles that can produce electric and magnetic fields.
The source of all electromagnetic waves is charge that is changing speed or direction.
Other types of electromagnetic waves are also created in atoms. Which are electrons and gamma rays.
THE ELECTROMAGNETIC SPECTRUM
Electromagnetic waves are often arranged in order of wavelength and frequency and what is known and the electromagnetic spectrum.
The electromagnetic spectrum ranges from very long wavelengths, low frequency radio waves to very short wavelength, high frequency gamma rays.
The waves in the electromagnetic spectrum that have the lowest frequency and the longest wavelengths are called radio waves.
Radio waves are produced when charged particles move back and forth in instruments such as antennae.
The variation in either amplitude or frequency of a wave is called modulation.
The setting on your radio indicates the type of modulation used to carry information to your radio: AM means amplitude modulation, and FM means frequency modulation.
One particular group of radio waves is that of microwaves. Microwaves are the highest frequency radio waves.
Short wavelength microwaves re used in radar. Radar, which stands for radio detecting and ranging, is used to locate objects and monitor speed. Radar is used to keep track of satellites that are orbiting the Earth.
Electromagnetic waves with frequencies with frequency slightly lower than visible light are called infrared rays. Although infrared rays cannot be seen, they can be felt as heat.
The electromagnetic waves that you can see are called visible light. Notice that visible light – red, orange, yellow, green, blue, indigo, violet- is an extremely small portion of the spectrum. The rest of the electromagnetic spectrum is invisible to the unaided eye.
Life on earth could not exist without visible light.
Electromagnetic wave with frequencies just higher than visible light are called ultraviolet rays. The energy of ultraviolet rays is great enough to kill living cells. So ultraviolet rays are often used to kills germs in hospitals and to destroy bacteria and preserve food in processing pants.
Although ultraviolet rays are invisible to humans and many other animals, it can be seen by many insects.
Ultraviolet rays are present in sun light, although we can’t see them we can fell their effects in sunburns. Fortunately, the earth’s O-Zone layer absorbs most of the sun’s damaging ultraviolet rays. Without this layer, life on earth would be impossible.
Ultraviolet rays help the body produce vitamin D, which is needed to make healthy bones and teeth.
Electromagnetic waves with frequencies just above ultraviolet rays are called X-rays. The energy of X-rays are great enough to pass through many materials, including your skin. Denser materials though, like your bones, absorb X-rays, which allows a picture to be taken of your bones.
Exploding stars are known to give off most energy in the form of X-rays.
Despite their usefulness, X-rays are potential health hazards. Exposure to x-rays over a life time can cause defects in cells. Lead absorbs most X-rays, therefore, it is used to protect our body’s when dealing with X-rays.
The electromagnetic waves with the highest frequencies and shortest wavelengths are called gamma rays.
Anything that can give off its own light is called a luminous object.
An object that can be seen because it is lit up is call and illuminated object
PRODUCTION OF LIGHT
Three types of light that can be produced by a luminous object are incandescent light, fluorescent light, or neon light.
Light that is produced from heat is called incandescent light.
Fluorescent light is light produced by bombarding molecules of gas in a tube.
Neon light is cool light produced when electrons flow through a glass tube filed with gas.