A Level Physics Waves Explained: Complete Concept Guide
A Level Physics Waves Explained: Complete Concept Guide
Waves are fundamental to understanding many phenomena in A Level Physics. This complete guide explains wave properties, types of waves, wave behaviors, and applications, with clear explanations and practical examples.
What are Waves?
Waves transfer energy without transferring matter. They involve:
- Oscillation: Regular back-and-forth motion
- Energy Transfer: Energy moves through medium
- No Net Movement: Particles oscillate but don’t move with wave
Key Characteristics:
- Transmit energy
- Can travel through different media
- Exhibit specific behaviors (reflection, refraction, diffraction)
- Can interfere with each other
Wave Properties
Wavelength (λ)
- Distance between two identical points on wave
- Measured in meters (m)
- Crest to crest or trough to trough
- Shorter wavelength = higher frequency
Frequency (f)
- Number of waves per second
- Measured in Hertz (Hz)
- 1 Hz = 1 wave per second
- Higher frequency = shorter wavelength
Amplitude (A)
- Maximum displacement from equilibrium
- Measured in meters (m)
- Related to energy: E ∝ A²
- Larger amplitude = more energy
Period (T)
- Time for one complete wave
- Measured in seconds (s)
- T = 1/f (period = 1/frequency)
- Related to frequency
Speed (v)
- How fast wave travels
- Measured in m/s
- v = fλ (speed = frequency × wavelength)
- Depends on medium
Wave Equation
The Fundamental Equation:
- v = fλ
- Speed = frequency × wavelength
- If you know two, can find third
- Speed depends on medium, not frequency
Examples:
- If f = 50 Hz and λ = 2 m, then v = 50 × 2 = 100 m/s
- If v = 340 m/s and f = 1000 Hz, then λ = 340/1000 = 0.34 m
Types of Waves
Transverse Waves
- Particles oscillate perpendicular to wave direction
- Examples: light, water waves, electromagnetic waves
- Can be polarized
- Crests and troughs
Longitudinal Waves
- Particles oscillate parallel to wave direction
- Examples: sound, seismic P-waves
- Compressions and rarefactions
- Cannot be polarized
Key Differences:
- Transverse: perpendicular oscillation
- Longitudinal: parallel oscillation
- Both transfer energy
- Both follow v = fλ
Wave Behaviors
Reflection
- Wave bounces off surface
- Angle of incidence = angle of reflection
- Can form standing waves
- Examples: echo, mirrors
Refraction
- Wave changes direction when entering new medium
- Due to change in speed
- Wavelength changes, frequency stays same
- Examples: light through glass, sound through different temperatures
Diffraction
- Wave spreads out after passing through gap or around obstacle
- More diffraction if wavelength similar to gap size
- Explains why we can hear around corners
- Examples: sound around door, light through small slit
Interference
- Two waves combine
- Constructive: waves add (larger amplitude)
- Destructive: waves cancel (smaller amplitude)
- Depends on phase difference
- Examples: beats in sound, interference patterns
Standing Waves
What are Standing Waves?
- Formed when two identical waves travel in opposite directions
- Nodes: points of no displacement
- Antinodes: points of maximum displacement
- Stationary pattern (doesn’t travel)
Formation:
- Wave reflects and interferes with itself
- Specific frequencies form standing waves
- Harmonics: fundamental and overtones
- Examples: guitar strings, organ pipes
Applications:
- Musical instruments
- Resonance
- Frequency determination
- Wave analysis
Electromagnetic Waves
Electromagnetic Spectrum:
- Radio waves: longest wavelength, lowest frequency
- Microwaves
- Infrared
- Visible light
- Ultraviolet
- X-rays
- Gamma rays: shortest wavelength, highest frequency
Properties:
- All travel at speed of light (c = 3 × 10⁸ m/s)
- Transverse waves
- Can travel through vacuum
- Energy increases with frequency
Uses:
- Radio: communication
- Microwaves: cooking, radar
- Infrared: heating, remote controls
- Visible light: vision, photography
- Ultraviolet: sterilization, tanning
- X-rays: medical imaging
- Gamma rays: cancer treatment
Sound Waves
Properties:
- Longitudinal waves
- Require medium (can’t travel in vacuum)
- Speed: ~340 m/s in air (depends on temperature)
- Frequency determines pitch
- Amplitude determines loudness
Doppler Effect:
- Frequency changes when source moves
- Moving toward: higher frequency (higher pitch)
- Moving away: lower frequency (lower pitch)
- Examples: ambulance siren, radar
Applications:
- Communication
- Music
- Sonar
- Ultrasound imaging
Common Mistakes to Avoid
1. Confusing Wave Speed and Frequency
- Speed depends on medium
- Frequency depends on source
- v = fλ always applies
- Changing medium changes speed and wavelength, not frequency
2. Wave Direction vs Particle Motion
- Wave direction: direction energy travels
- Particle motion: direction particles oscillate
- Different for transverse and longitudinal
3. Not Understanding Interference
- Constructive: waves in phase, add together
- Destructive: waves out of phase, cancel
- Depends on path difference
Related Resources
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Written by
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Educational Content Specialists
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