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The electromagnetic spectrum
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Light is one small part of a family of electromagnetic waves that all travel at the same speed in a vacuum.
The spectrum
In order of increasing frequency (decreasing wavelength):
radio, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays
Visible light runs from red (longest wavelength) to violet.
radio, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays
Visible light runs from red (longest wavelength) to violet.
Shared properties
All are transverse waves.
All travel at the speed of light, 3 × 108 m/s, in a vacuum.
They transfer energy from the source to an absorber.
All travel at the speed of light, 3 × 108 m/s, in a vacuum.
They transfer energy from the source to an absorber.
Energy and frequency
Higher frequency means more energy. Ultraviolet, X-rays and gamma rays are ionising, so they can damage cells.
A radio wave has frequency 100 MHz. Find its wavelength.
- v = fλ, so λ = v ÷ f
- λ = 3 × 108 ÷ 1 × 108
Answer: 3 m
Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma: increasing frequency and energy. All are transverse and travel at 3 × 108 m/s in a vacuum.
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