Waves
Properties of waves, sound, and the electromagnetic spectrum
Types of waves:
- Transverse: oscillations perpendicular to wave direction (light, EM waves, water waves)
- Longitudinal: oscillations parallel to wave direction (sound, ultrasound)
Key terms:
- Amplitude (A): maximum displacement from equilibrium (height of wave)
- Wavelength (λ): distance between two identical points on adjacent waves
- Frequency (f): waves passing a point per second (Hz)
- Period (T): time for one complete wave (T = 1/f)
Wave equation: **v = fλ** (wave speed = frequency × wavelength)
Sound: longitudinal wave, needs a medium (can't travel in vacuum). Speed in air ~340 m/s.
The electromagnetic spectrum (increasing frequency / decreasing wavelength):
Radio → Microwaves → Infrared → Visible light → UV → X-rays → Gamma rays
All travel at 3 × 10⁸ m/s in a vacuum.
Reflection: angle of incidence = angle of reflection (measured from normal).
Refraction: waves bend when speed changes (entering glass, light slows → bends towards normal).
Key Points to Remember
- 1Transverse: oscillation perpendicular; Longitudinal: parallel
- 2v = fλ (wave speed = frequency x wavelength)
- 3EM spectrum: radio to gamma, all at 3x10^8 m/s in vacuum
- 4Reflection: angle in = angle out; Refraction: speed change causes bending
Pakistan Example
Mobile Phones and the EM Spectrum in Pakistan
Every phone in Pakistan uses the EM spectrum: FM radio (radio waves), WiFi and Bluetooth (microwaves), remote controls (infrared), visible light displays, hospital X-rays, and Cobalt-60 cancer treatment (gamma rays). Jazz 4G networks use frequencies around 1800 MHz — those are microwaves with v = fλ. Understanding the EM spectrum explains why Karachi gets better radio reception in certain areas.
Quick Revision Infographic
Physics — Quick Revision
Waves
Key Concepts
Formulas to Know
wave speed = frequency x wavelength)8 m/s in vacuumReflection: angle in = angle out; Refraction: speed change causes bendingMobile Phones and the EM Spectrum in Pakistan
Every phone in Pakistan uses the EM spectrum: FM radio (radio waves), WiFi and Bluetooth (microwaves), remote controls (infrared), visible light displays, hospital X-rays, and Cobalt-60 cancer treatment (gamma rays). Jazz 4G networks use frequencies around 1800 MHz — those are microwaves with v = fλ. Understanding the EM spectrum explains why Karachi gets better radio reception in certain areas.