4PH1

Waves & The Electromagnetic Spectrum

Waves · 1 question type

Practise

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 14% of your exam marks.

stable
High
Stable14%

Wave equation (v = fλ), transverse vs longitudinal and EM spectrum properties tested consistently.

The basic equation

v = f × λ

  • where:
    • v = wave speed (m/s)
    • f = frequency (Hz)
    • λ = wavelength (m)
  • The equation applies to every kind of , including sound, water ripples, and every band of the electromagnetic spectrum
  • Rearrangements:
    • λ = v / f (a higher-frequency wave has a shorter wavelength at fixed speed)
    • f = v / λ

Linking frequency to period

f = 1 / T

  • When a question gives you the period rather than the frequency, find f first, then use the wave equation
Worked example

Calculating frequency using the wave equation

A radio signal travels at 3.0 × 10⁸ m/s and has a wavelength of 1.5 m. Calculate the frequency of the signal.

Solution:

  • Write the wave equation: v = f × λ
  • Rearrange for frequency: f = v ÷ λ
  • Substitute: f = 3.0 × 10⁸ ÷ 1.5
  • = 2.0 × 10⁸ Hz