Optics & Waves · GCSE Physics Topic 6 (Sound Waves)
Sound Wave Characteristics & Oscilloscope Simulator
Key exam takeaway: Pitch is determined by frequency (wave density); loudness by amplitude (wave crest height); timbre by harmonic waveform shape. Sound cannot travel in vacuum.
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Live Derivations & Metrics
Wave Period T
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Speed of Sound v
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Acoustic Wavelength λ
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Audibility Category
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Real-Time Formula Derivation
Governing Formula:
--Substitution:
--Regime: --
Worked Examples & Exam Question Deep Dive
Worked Problem
Problem: In 15°C air (v=340m/s), what are the period and wavelength of a 1000Hz sound?
Step-by-Step Derivation:
- Period T = 1/f = 1ms. Wavelength λ = v/f = 340/1000 = 0.34m = 34cm.
Worked Problem
Problem: Wave A oscillates 500 times/s with 2cm amplitude; Wave B oscillates 1000 times/s with 1cm amplitude. Compare pitch and loudness.
Step-by-Step Derivation:
- Wave B has higher frequency (1000Hz > 500Hz) so higher pitch. Wave A has larger amplitude (2cm > 1cm) so greater loudness.
Student Inquiry Worksheet & Practice Problems
Q1. Variant 1: Striking a tuning fork harder changes what on the oscilloscope? What changes and what stays constant?
Answer Key: Wave crest amplitude increases; wave density (frequency) stays identical. Loudness increases; pitch and timbre remain unchanged.
Q2. Variant 2: When pouring boiling water into a thermos, does the sound pitch rise or fall? Why?
Answer Key: Pitch rises higher. Rising water level shortens the vibrating air column, raising its resonant frequency.
Q3. Variant 3: What is human audible hearing range? What are the frequency ranges of ultrasound and infrasound?
Answer Key: Human range: 20Hz - 20,000Hz. Ultrasound > 20,000Hz (bats, sonar). Infrasound < 20Hz (earthquakes, tsunamis).
Frequently Asked Questions & Misconceptions
In common language, does "singing high and low" refer to pitch or loudness?
It refers to loudness (volume)! Everyday speech confuses loud with high. In physics, "pitch" strictly refers to acoustic frequency.
Can sound travel in vacuum? How do astronauts talk on Moon?
Sound strictly cannot travel in vacuum. Astronauts communicate via electromagnetic radio waves, or touching helmets for solid conduction.
What is sonar echo ranging? What minimum distance is needed to distinguish an echo?
Ears need 0.1s gap between original and reflected sound. Minimum distance s = 0.5 * 340 * 0.1 = 17m.
How do Active Noise Cancelling (ANC) headphones eliminate noise?
Acoustic wave cancellation! Microphones detect noise and emit an anti-phase inverted soundwave (180° offset), cancelling sound pressure.