Q. Sound waves travel at 350 m/s through warm air and at 3500 m/s through brass. The wavelength of a 700 Hz acoustic wave as it enters brass from warm air
A) Decreases by a factor 20
B) Decreases by a factor 10
C) Increases by a factor 20
D) Increases by a factor 10
Explanation
[Solution from source] Frequency is unchanged when a wave enters a new medium, so λ = v/f is proportional to speed. λ goes from 350/700 = 0.5 m to 3500/700 = 5 m, an increase by a factor of 10. It increases, not decreases, because sound is faster in brass. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.