General Wave Properties
Section: Waves | Syllabus: Cambridge AS Level Physics 9702
What are Waves? A wave is a disturbance that transfers energy from one place to another without transferring matter . Think of it like this: when you throw a stone into a pond, the water doesn't travel outward-only the energy does, creating ripples that spread across the surface.
Wave A disturbance that transfers energy from one place to another without transferring matter. Key Point Waves transfer energy , not matter. The particles of the medium vibrate in place while the wave pattern moves forward.
Diagram Placeholder [Diagram showing energy transfer through a wave with particles oscillating in place - to be added] Features of Waves Every wave has specific characteristics that we can measure and describe.
Understanding these features is essential for analyzing all types of waves. 1. Amplitude (A) Amplitude The maximum displacement of a point on the wave from its rest (equilibrium) position. What it represents: The energy carried by the wave-larger amplitude = more energy Unit: metres (m) Example: A louder sound has greater amplitude; a brighter light has greater amplitude 2.
Wavelength (λ) Wavelength The distance between two consecutive corresponding points on a wave (e.g., crest to crest, or trough to trough). Symbol: λ (Greek letter "lambda") Unit: metres (m) How to measure: From one peak to the next peak, or from one compression to the next compression 3.
Frequency (f) Frequency The number of complete waves (or cycles) passing a point per second. Unit: hertz (Hz), where 1 Hz = 1 wave per second What it affects: In sound, frequency determines pitch (high frequency = high pitch).
In light, frequency determines color 4. Period (T) Period The time taken for one complete wave to pass a point. Unit: seconds (s) Relationship: T = 1/f (period is the inverse of frequency) 5. Wave Speed (v) Wave Speed How fast the wave travels through the medium.
Unit: metres per second (m/s) What it depends on: The properties of the medium (e.g., sound travels faster in solids than in air) Diagram Placeholder [Labeled diagram of a transverse wave showing amplitude, wavelength, crest, trough, and rest position - to be added] Wave Features Summary Feature Symbol Unit What It Measures Amplitude A metres (m) Maximum displacement / Energy Wavelength λ metres (m) Distance between repeating points Frequency f hertz (Hz) Waves per second Period T seconds (s) Time for one complete wave Wave Speed v m/s Speed of wave propagation The Wave Equation The wave equation is one of the most important relationships in physics.
It connects three fundamental wave properties: speed, frequency, and wavelength. v = fλ Where: \(v\) = wave speed (m/s) \(f\) = frequency (Hz) \(λ\) = wavelength (m) Understanding the Equation Think of it like this: Frequency (f) tells you how many waves pass per second Wavelength (λ) tells you how long each wave is Multiply them together and you get how far the wave pattern travels in one second = wave speed (v) Memory Trick: " Very Fast Lambs " → v = f × λ Worked Examples Example: Finding Wave Speed Question: A wave has a frequency of 50 Hz and a wavelength of 2 m.
What is its speed? Solution Given: \(f = 50\) Hz, \(λ = 2\) m v = fλ v = 50 × 2 = 100 m/s Example: Finding Wavelength Question: Sound waves travel at 330 m/s with a frequency of 440 Hz. Calculate the wavelength.
Solution Given: \(v = 330\) m/s, \(f = 440\) Hz Rearrange: \(λ = v/f\) λ = 330/440 = 0.75 m Example: Finding Frequency Question: Light waves have a wavelength of 600 nm (6 × 10⁻⁷ m) and travel at 3 × 10⁸ m/s.
Find the frequency. Solution Given: \(λ = 6 × 10^-7\) m, \(v = 3 × 10^8\) m/s Rearrange: \(f = v/λ\) f = 3 × 10^8/6 × 10^-7 = 5 × 10^14 Hz Ripple Tank Experiments A ripple tank is a shallow transparent tank of water used to study wave behavior.
It's one of the most powerful demonstrations in physics because it makes invisible wave principles visible! What Is a Ripple Tank? A ripple tank consists of: Shallow glass or plastic tank filled with water (few cm deep) Light source above the tank White screen or paper below to observe wave shadows Wave generator (vibrating bar or dipper) to create waves How It Works: Light shines through the water Wave crests act like converging lenses → bright lines on screen Wave troughs act like diverging lenses → dark lines on screen The pattern on the screen shows the wave pattern in the tank Key Experiments & Observations Experiment 1: Measuring Wave Speed Method: Generate straight plane waves in the tank Count the number of waves (n) passing a point in time (t) Calculate frequency: f = n/t Measure wavelength (λ) from the pattern on the screen Calculate speed: v = f × λ Experiment 2: Investigating Reflection Setup: Place a straight barrier in the tank Observations: Waves bounce back from the barrier Angle of incidence = angle of reflection Wavelength and frequency unchanged Using a curved barrier creates focusing effects Experiment 3: Investigating Refraction Setup: Place a glass or plastic sheet under the water to…
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