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Electromagnetic Waves
• Electromagnetic waves are transverse waves consisting of changing electric and magnetic fields.
• Energy travels in the form of waves.• They can travel in a vacuum as well as
through matter. • Electromagnetic radiation- the transfer of energy by electromagnetic waves traveling through matter or across space.
Light, like sound and heat, is a form of energy.
The visible light we see is part of the electromagnetic spectrum.
Things to know…
• frequency– how often a wave passes a point in a certain time interval
• wavelength- the distance from one crest to the next or one trough to the next
The speed of light depends on the medium.
• The speed of light in a vacuum is: 3 X 108 meters per second (300,000,000 m/sec)
Electromagnetic Spectrum- the full range of frequencies of electromagnetic radiation.
This spectrum includes visible light and invisible waves:• radio wave• microwaves• infrared light• ultraviolet light• X-rays• gamma rays
The Electromagnetic Spectrum
Wavelength and Frequency
Wavelength and Frequency of Light
Because the wavelength of light is so small, scientists measure it in nanometers.
One nanometer (nm) is one billionth of a meter (0.000000001 m).
The electromagnetic spectrum includes:
Radio Waves• Has the longest wavelength and the
lowest frequency.• Uses: Radio, TV, radar, microwaves
– Radar: radio detection and ranging, a system that uses reflected radio waves to determine the velocity and location of objects
Microwaves• Microwaves are used in cooking and
communication.– Microwaves have wavelengths in the
range of centimeters.
Infrared Rays• Wavelength smaller than radio.• slightly longer than red visible light.• felt as warmth• Used as a source of heat/or to detect heat
differences.• Thermograms- color-coded pictures that show variations in temperature.
Visible Light• Each wavelength in the visible
spectrum corresponds with a specific frequency and a specific color.
• Light enables people to see, keeps people safe and helps them to communicate.
Ultraviolet Rays• Shorter wavelength and higher
frequency than violet light.• Sunlight contains ultraviolet light.
– The invisible light that lies just beyond violet light falls into the ultraviolet (UV) portion of the spectrum.
X-Rays• Have very short wavelengths.• Less than 10–8 m.
• Used in medicine, industry and
transportation by making pictures of the inside of
solid objects.
Gamma Rays• Shortest wavelength in the
electromagnetic spectrum.• wavelengths shorter than 10–10 m.
• Have the highest frequency.• Have the most energy.• Over exposure can be
deadly.• Used in the medical field
to kill cancer cells and make pictures of the brain, and in industrial situations as an inspection tool.