The wave equation
2 marks · EasyWhat happens to the wavelength of a wave if its frequency is halved, but its speed stays the same? Explain your answer.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
The wavelength doubles.
Also accept: Wavelength becomes twice as long; If frequency halves and speed is constant, wavelength doubles
Common mistakes: Wavelength halves; Wavelength stays the same
Show mark scheme and worked solution
Marking points
B1 · 1 mark · States wavelength doubles (or equivalent).
B1 · 1 mark · Mentions use of v = f × λ, or explains that if v is constant and f halves, λ must double.
Worked solution
The wavelength doubles because v = f × λ and wave speed stays the same, so if frequency halves, wavelength must double to keep v the same.