EM Waves
Physics · विद्युत चुंबकीय तरंगें
📋Quick Overview
Electromagnetic (EM) waves are waves made of oscillating electric and magnetic fields. They do NOT need any medium — they can travel through vacuum. All EM waves travel at the speed of light: 3 × 10⁸ m/s. James Clerk Maxwell predicted them, and Heinrich Hertz proved them experimentally. The EM spectrum arranges all EM waves by their wavelength/frequency.
📖The Electromagnetic Spectrum
| EM Wave | Wavelength Range | Discovered By | Major Uses |
|---|---|---|---|
| Radio Waves | LONGEST (>1mm to km) | Heinrich Hertz | AM/FM radio, TV broadcasting, communication |
| Microwaves | 1mm to 1m | Hertz | Microwave oven, RADAR, satellite communication, mobile phones |
| Infrared (IR) | 700nm to 1mm | William Herschel | TV remote, night vision cameras, thermal imaging, heat lamps |
| Visible Light | 400nm to 700nm | Isaac Newton (prism) | Seeing! VIBGYOR colors, photography |
| Ultraviolet (UV) | 10nm to 400nm | Johann Ritter | Sterilization, vitamin D production, currency checking, sunburn cause |
| X-Rays | 0.01nm to 10nm | Wilhelm Rontgen | Medical imaging (bones), airport security, detecting fractures |
| Gamma Rays | SHORTEST (<0.01nm) | Paul Villard | Cancer treatment, food preservation, sterilization, nuclear reactions |
⭐
KEY ORDER: Radio > Micro > IR > Visible > UV > X > Gamma (wavelength DECREASING). Frequency and energy INCREASE in opposite direction: Gamma has highest frequency & energy, Radio has lowest.
📝Key Facts about EM Waves
- •All EM waves travel at speed of light (c = 3 × 10⁸ m/s) in vacuum
- •EM waves are transverse waves (electric and magnetic fields perpendicular to direction of travel)
- •EM waves don't need medium — can travel through vacuum (unlike sound)
- •Ozone layer protects us from harmful UV rays from the Sun
- •RADAR (Radio Detection And Ranging) uses microwaves to detect aircraft and measure speed
- •TV remote control uses infrared (IR) rays
- •UV rays cause skin tan/sunburn and help body make Vitamin D