The electromagnetic spectrum is the complete range of different wavelengths of electromagnetic radiation. Electromagnetic radiation is a kind of energy which has properties created both by an electric field and a magnetic field. The energy of these two different fields act perpendicular to one another, creating the wave-like oscillation of electromagnetic radiation. Visible light is an example of electromagnetic radiation. Short wavelength, high frequency radiation has more energy than long wavelength, low frequency radiation.
Radio Waves
Radio waves have the longest wavelengths, and lowest frequencies of any type of electromagnetic radiation. Different frequencies of radio waves are used for different types of communication, including radio, television and cell phone. Every television station or radio station has a separate frequency of radio waves which they broadcast from.
Types of radio waves:
- AM - "amplitude modulated," 500-1500 kHz
- short wave, 1.605 - 54 MHz
- TV and FM, 54-1600 MHz
- cellular, 824.040 - 848.970 MHz
Microwaves
Microwaves are next on the electromagnetic spectrum, ranging from 1.6-30 GHz. Microwaves still have a relatively long wavelength, making them less energetic than other types of waves. Though microwaves have low energy, they are easily absorbed by water, allowing them to efficiently heat up food and drinks. Microwaves which heat up food operate at 2450 MHz.
Radar
Radar uses frequencies within the microwave range, but has a completely different application. Radar, which is short for "radio detection and ranging," works by sending out a microwave from an antennae and tracking it as it bounces off of objects or surfaces. By measuring aspects of the returning wave, properties of the surface or object it bounced off of are determined.
Infrared
Infrared radiation is the heat you feel whenever you touch a warm object. Everything that radiates heat radiates infrared radiation. Though we are unable to see infrared waves with the naked eye, night vision goggles and infrared detectors allow us to view this type of radiation. Infrared waves range from .003 - 4 x 10^14 Hz.
Visible Light Spectrum
The visible spectrum ranges from 4 - 7.5 x 10^14 Hz. Red light is the longest wavelength type of visible light, followed by orange, yellow, green blue, indigo and violet. The color we see from various objects actually represents the type of radiation being bounced off of that object. For example, a red apple absorbs all types of visible light except for red frequency light. As the red waves bounce back from the apple, we perceive it as red.
Ultraviolet
Ultra violet radiation, or UV rays, are a component of sunlight. These rays are energetic enough to harm biological materials, and range from 7.5 x 10^14 - 3 x 10^16 Hz. Overexposure to UV rays leads to sunburn in the short term, and contributes to skin cancer risks over time. UV exposure may also lead to cataracts and premature wrinkling of the skin.
X-Rays
X-rays, ranging from 3 x 10^16 Hz and up, are commonly used in small amounts for medical purposes. X-ray usefulness comes from its ability to penetrate materials that visible light can not go through. For example, X-rays are able to penetrate skin and soft tissue organs, revealing the bones of the skeletal system underneath. Frequent exposure to X-rays increases the risk of cancer, as X-rays are relatively high energy radiation.
Gamma Rays
Gamma rays are the highest energy form of radiation, having short wavelengths and high frequencies. Ranging from 10^20 Hz and above, gamma rays are produced by stars, including our sun. Some unstable atomic nuclei on earth also give off gamma rays, which are highly damaging to human tissues.
Resources
Earth.rice.edu. "Characteristics of Radar" (Accessed March 15, 2011).
Hyperphysics.phy-astr.gsu.edu. "Electromagnetic Spectrum." (Accessed March 15, 2011).
Science.hq.nasa.gov. "Radio Waves" (Accessed March 15, 2011).
Tro, Nivaldo J. "Principles of Chemistry, A Molecular Approach." Pearson Education, 2010.
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