Light and Sound
4 marks · EasyA student studies wave properties using a sound wave and a light wave.
The student sets up a sound wave with a frequency of 100 Hz and speed 340 m/s. Calculate its wavelength.
On an oscilloscope, the student sees two traces: - Trace A has high frequency and large amplitude. - Trace B has low frequency and small amplitude. Explain the difference in pitch and loudness between the two traces.
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
(a) Wavelength = speed / frequency = 340 / 100 = 3.4 m · must show Correct calculation, Correct unit
(b) Trace A: higher pitch (because high frequency) and louder (large amplitude). Trace B: lower pitch (lower frequency), quieter (smaller amplitude). · must show Pitch linked to frequency, Loudness linked to amplitude, Statements for both traces
Common mistakes: Mixing up pitch and loudness; Incorrect wavelength formula
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Writes wavelength formula (speed = frequency × wavelength, or wavelength = speed / frequency).
A1 (a) · 1 mark · Correct calculation (3.4 m, ±0.2).
B1 (b) · 1 mark · Relates high frequency to higher pitch, large amplitude to louder sound for Trace A.
B2 (b) · 1 mark · Relates low frequency and small amplitude to lower pitch and quieter sound for Trace B.
Worked solution
a) Wavelength = speed / frequency = 340 m/s ÷ 100 Hz = 3.4 m
b) Trace A, with high frequency and large amplitude, is high-pitched and loud. Trace B, with low frequency and small amplitude, is lower-pitched and quieter.