Tuesday, 26 August 2025

Week 7 Term 3 2025 Waves & Basic Wave Properties

Homework:

Act 5A, p,53, Pulses and Waves
Ex 3D, p.66--67, Wave Properties
Ex 3F, p.3F, p.73-75 Superposition
Act 5B, p. 58, Reflection, Refraction and Diffraction of Waves
Act 5C, p.63-64, Diffraction and Superposition

Basic Properties of Waves

waves transfer energy through a medium without transferring the medium itself

Cycle - a basic repeating unit in a wave
Amplitude A (m) - the distance from the middle point to the top of a crest, or bottom of a trough
Wavelength 𝜆 (m) - the distance/length of one cycle
Period T (s = s per cycle) - the time it takes for one cycle to pass a point
Frequency f (Hz = cycles per second) - the number of cycles that pass in one second

T = 1/f & f = 1/T

Wave Speed v (ms-1) the speed of a wave

v = 𝜆/T & v = f𝜆

Wave Properties

Frequency & Period

Wave Phase

Pendulum Waves

Longitudinal Waves

particle displacement in the medium is parallel to the direction of wave propagation e.g. sound waves, primary earthquake waves

Transverse Waves

particle displacement in the medium is perpendicular to the direction of wave propagation e.g. light and other electromagnetic waves, secondary earthquake waves

Superposition of Waves: two waves traveling through each other will not change each other motion in any way, but they will add to one another when they overlap

Constructive Interference - Reinforcement - In Phase
Destructive Interference - Cancellation - Out of Phase

PhET Waves on a String App - link

Reflection on A String

Hard Boundary

Wave reflects on opposite side (opposite phase)

Same Amplitude, A

Same Wavelength, 𝛌

Same Wave Speed, v

Reflection on A String

Soft Boundary

Wave reflects on same side (same phase)

Same Amplitude, A

Same Wavelength, 𝛌

Same Wave Speed, v

Refraction on A String

Fast to Slow Boundary

Relation of waves to Incident Wave

Reflected Wave - same speed - same wavelength 𝛌 - opposite phase

Refracted Wave - slower speed - smaller wavelength 𝛌 - same phase

Refraction on A String

Slow to Fast Boundary

Relation of waves to Incident Wave

Reflected Wave - same speed - same wavelength 𝛌 - same phase

Refracted Wave - faster speed - larger wavelength 𝛌 - same phase

Diffraction

The Bending of Waves Around Corners
Larger Wavelength, 𝛌 - greater the angle of diffraction
Shorter Wavelength, 𝛌 - smaller the angle of diffraction
Also the smaller the gap the greater the angle of diffraction