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⚑ Types of Electromagnetic Waves

Spec 6.6.2.1 πŸ“™ Higher
πŸ“– In-Depth Theory

The Electromagnetic Spectrum

ELECTROMAGNETIC (EM) WAVES are transverse waves that transfer energy from source to absorber.
All EM waves:
Travel at the SAME SPEED in vacuum: c = 3 Γ— 10⁸ m/s.
Are TRANSVERSE waves.
Can travel through a VACUUM (no medium needed).
Transfer ENERGY.
EM waves form a CONTINUOUS SPECTRUM grouped by wavelength and frequency:
(longest wavelength / lowest frequency β†’ shortest wavelength / highest frequency)
RADIO WAVES β†’ MICROWAVES β†’ INFRARED β†’ VISIBLE LIGHT β†’ ULTRAVIOLET β†’ X-RAYS β†’ GAMMA RAYS
Memory: 'Raging Martians Invaded Venus Using X-ray Guns'
As you go from radio β†’ gamma:
Wavelength DECREASES
Frequency INCREASES
Energy INCREASES (∝ frequency)

Wavelengths and Frequencies

Approximate ranges:
RADIO WAVES: λ = 0.1 m to 10⁴ m; f = 30 MHz to 3 kHz
MICROWAVES: Ξ» = 1 mm to 0.1 m; f = 300 MHz to 300 GHz
INFRARED: Ξ» = 700 nm to 1 mm
VISIBLE LIGHT: Ξ» = 400 nm (violet) to 700 nm (red)
ULTRAVIOLET: Ξ» = 10 nm to 400 nm
X-RAYS: Ξ» = 0.01 nm to 10 nm
GAMMA RAYS: Ξ» < 0.01 nm; highest frequency and energy
VISIBLE SPECTRUM (Roy G Biv):
Red β†’ Orange β†’ Yellow β†’ Green β†’ Blue β†’ Indigo β†’ Violet
Red has longest wavelength / lowest frequency in visible range.
Violet has shortest wavelength / highest frequency in visible range.

Sources and Properties

RADIO WAVES: produced by oscillating electrical circuits in transmitters.
MICROWAVES: produced by electronic devices; also by oscillating electrons.
INFRARED: emitted by all objects with temperature above absolute zero β€” thermal radiation.
VISIBLE LIGHT: produced by hot objects (incandescent), LEDs, fluorescent lamps.
ULTRAVIOLET: produced by very hot objects (the Sun), UV lamps.
X-RAYS: produced by decelerating high-energy electrons hitting a metal target.
GAMMA RAYS: emitted from unstable atomic nuclei during radioactive decay.
All are produced by changes in energy levels of electrons OR by oscillating charges.
All travel at 3 Γ— 10⁸ m/s in vacuum β€” but SLOWER in other materials.
Light slows down in glass β†’ this causes refraction.
⚠️ Common Mistake

All EM waves travel at the SAME speed in vacuum (3 Γ— 10⁸ m/s) β€” they differ only in wavelength and frequency. Higher frequency = shorter wavelength = more energy per photon. Gamma rays are NOT the same as X-rays β€” they come from different sources (nucleus vs electron deceleration).

πŸ“ Variables
cSpeed of EM waves in vacuum (c) is measured in m/s (3 Γ— 10⁸ m/s)
Ξ»Wavelength (Ξ») is measured in metres (m)
fFrequency (f) is measured in hertz (Hz)
πŸ“ Key Equations
c = f Γ— Ξ» (for EM waves in vacuum, c = 3 Γ— 10⁸ m/s)
πŸ“Œ Key Note

EM spectrum (longβ†’short Ξ»): radio, microwave, infrared, visible, UV, X-ray, gamma. All travel at 3Γ—10⁸ m/s in vacuum. All transverse. Higher frequency = shorter Ξ» = more energy. Visible: red (longest) to violet (shortest). Gamma from nucleus; X-rays from electron deceleration.

🎯 Matching Activity β€” EM Spectrum Order

Match each EM wave type to its wavelength range or key property. β€” drag the symbols on the right to match the component names on the left.

Radio waves
Drop here
Microwaves
Drop here
Infrared
Drop here
Visible light
Drop here
Gamma rays
Drop here
Emitted by all warm objects β€” detected as heat; used in night vision and remote controls
Longest wavelength β€” used for communication, TV and radio broadcasts
Shortest wavelength, highest energy β€” emitted by unstable atomic nuclei
Wavelength ~1 mm to 0.1 m β€” used in mobile phones, cooking, satellite communication
400 nm (violet) to 700 nm (red) β€” only part of EM spectrum detected by human eyes
🎯 Test Yourself
Question 1 of 2
1. Which EM wave has the highest frequency?
2. All electromagnetic waves in a vacuum have the same what?
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