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Electromagnetic waves

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by

Beatrice Leader

on 14 May 2015

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Transcript of Electromagnetic waves

Electromagnetic Spectrum
What is an electromagnetic wave?
Electromagnetic waves are waves that transport energy through space. These waves of energy are created by the vibration of electric charges. Depending on the density of an object, these waves can go through various materials; the more dense the substance, the harder it is for the waves to enter.
More Information on the Light Spectrum
How do we define Electromagnetic Waves?
Electromagnetic Waves
Different types of Electromagnetic Waves
Gamma rays
Gamma rays have the shortest wavelengths of all the electromagnetic waves but they contain the most energy.
Gamma rays are used during cancer treatment to kill cancerous cells.
The electromagnetic spectrum is the distribution of electromagnetic radiation according to energy (or equivalently, by virtue of the relations in the previous section, according to frequency or wavelength).

Each color in a rainbow corresponds to a different wavelength of electromagnetic spectrum.
Wavelengths in the Color Spectrum
Wavelength:
the distance between two successive peaks of a wave; normally measured in meters
The greater the energy of the electromagnetic waves, the larger the wave’s frequency and the shorter its wavelength
Hot objects emit their light in short wavelengths
Cold objects emit light in long wavelengths
The lights of each wavelength depends on the temperature of the object producing the light
Stars that are hotter than the Sun (more than 6,000 C) emit blue and ultraviolet light
Stars cooler than the Sun (below 5,000 C) emit red and infrared light
EM Waves &
Heat and Light
Radio Waves
Visible Light
Microwaves
Infrared
Ultraviolet
X-Rays
Gamma Rays
Radio Waves
Gamma Rays
Radio waves are the electromagnetic waves with the longest wavelengths and lowest frequency. Their wavelengths can range from the length of a football field to longer than planet Earth.

Frequency Range: <3 x 10^11 Hz
Wavelength Range: >1mm

Radio waves are used when listening to music on the radio (omg really?). When the radio is set to a specific frequency of a radio wave, the radio receives the radio waves and changes them into mechanical vibrations which we perceive as sound (or our favorite music).
Microwaves
Microwaves have a slightly shorter wavelength and higher frequency than radio waves.

Frequency Range: 3 x 10^11 - 10^13Hz
Wavelength Range: 1mm - 25um

Microwaves can vibrate water and fat molecules and heat them up, which is why they are used in "microwaves" to cook food. Microwaves are also used in mobile phones. Although microwaves are not that powerful, they can still harm us by creating cataracts in our eyes so that we can't see clearly and by affecting our brain development.

Are electromagnetic waves sine waves?
X-Rays
Electromagnetic waves are actually electrical pulses, but the repetition of these pulses can be displayed as a wave. This wave is a sine wave.
The "visible light" corresponds to a wavelength range of 400 - 700 nanometers (nm) and a color range of violet through red. The human eye is not capable of "seeing" radiation with wavelengths outside the visible spectrum.
In Other Words...
X-Rays are electromagnetic waves that are high energy with either "hard" (a.k.a. short) wavelengths or "soft" (a.k.a. long) wavelength.

Frequency Range: 10^17 - 10^20 Hz
Wavelength Range: 1nm - 1pm

X-rays are emitted from stars and some nebulas. They are used when producing an X-ray. An X-ray machine fires a beam of electrons at a "target". When the electrons are fired with enough energy, X-rays are produced.
Gamma rays have the shortest wavelength and highest frequency of the entire electromagnetic wave spectrum.

Frequency Range: 10^20 - 10^24 Hz
Wavelength Range: <10-12 m

Gamma rays are given off by stars, and pass through most materials except for concrete and lead. They are used in cancer treatments to kill cancer cells, but can also cause cancer and mutations in growing tissues.
Infrared Waves
Infrared radiation is between the visible and microwave portions of the electromagnetic spectrum.

Frequency Range: 1x10^13 - 4x10^14 Hz
Wavelength Range: 25um - 750nm

When you turn on your television, infrared waves are the waves that are used. The most well known infrared radiation is heat or thermal radiation. Infrared waves can also help heal sports injuries.
Visible light is at the center of the electromagnetic spectrum. It is the only range of wavelengths that is perceived by the human eye.

Frequency Range: 4x10^14 - 7.5x10^14 Hz Wavelength Range: 750nm - 400 nm
Visible Light
Ultraviolet
Ultraviolet radition can be split into the shorter wavelength far ultraviolet and the longer wavelength near ultraviolet.

Frequency Range: 10^15 - 10^17 Hz
Wavelength Range: 400nm - 1nm

Ultraviolet light is given off by the Sun, and can be artificially created by sun lamps. UV light is used to get a sun tan, detect forged bank notes, and detect the writings of a security marker pen. UV lamps are used by doctors to treat some skin disorders and Vitamin D deficiency, since the light can cause th e body to produce this vitamin.

Color Region
Wavelength (nm)
Violet
: 380-435
Blue
: 435-500
Cyan
: 500-520
Green
: 520-565
Yellow
: 565-590
Orange
: 590-625
Red
: 625-740
Frequency:
number of cycles of a wave per a second, measured in cycles per a second (Hertz)
Full transcript