0Definition:
Electromagnetic waves are waves that consist of oscillating electric and magnetic fields, which are perpendicular to each other and to the direction of wave propagation.
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They do not require a medium → can travel through vacuum.
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Discovered by James Clerk Maxwell, who predicted them using his Maxwell’s equations.
📌 Key Features of EM Waves
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Transverse Waves:
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Electric field (EEE) and magnetic field (BBB) are perpendicular to each other and to the direction of wave travel.
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Self-Propagating:
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Changing electric field produces magnetic field and vice versa → wave moves forward.
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Speed:
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In vacuum, they travel at speed of light (~3 × 10⁸ m/s).
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Do Not Need Medium:
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Unlike sound waves, EM waves can travel in space → this is how sunlight reaches Earth.
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Carry Energy and Momentum:
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EM waves can exert pressure (radiation pressure).
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They carry energy, which can be absorbed by matter.
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📌 Electromagnetic Spectrum
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EM waves are classified based on wavelength or frequency.
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Types (from longest to shortest wavelength / lowest to highest frequency):
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Radio waves – Communication, TV, radio
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Microwaves – Cooking, radar
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Infrared (IR) – Heaters, remote controls
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Visible light – Human vision, photography
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Ultraviolet (UV) – Sterilization, sunburn
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X-rays – Medical imaging
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Gamma rays – Cancer treatment, radioactive decay
Key Idea: Longer wavelength → lower energy; shorter wavelength → higher energy.
📌 Properties of EM Waves
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Transverse nature → EEE ⟂ BBB ⟂ propagation
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Speed is constant in vacuum
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Can travel through vacuum or transparent media
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Carry energy, momentum, and exert pressure
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Obey superposition principle → interference and diffraction possible
📌 Applications of EM Waves
| Type | Application |
|---|---|
| Radio waves | Radio, TV communication |
| Microwaves | Radar, microwave ovens |
| Infrared | Remote controls, heaters, night vision |
| Visible light | Vision, photography, lasers |
| Ultraviolet | Sterilization, tanning |
| X-rays | Medical imaging, material analysis |
| Gamma rays | Cancer treatment, nuclear physics |
📌 Quick Notes for Revision
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EM waves are transverse, self-propagating, and don’t need a medium.
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Electric and magnetic fields are perpendicular to each other and to wave direction.
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Travel at speed of light in vacuum.
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EM spectrum ranges from radio waves (low energy) to gamma rays (high energy).
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Applications cover communication, medical, cooking, and radiation therapy.
