Physics for IGCSE & O level - Waves And Sounds (Section 7 - No. 45)
What is the frequency of the ultrasound described in the boat echo sounder example if the wavelength is 0.035 m?
40 Hz
40 kHz
40 MHz
1400 Hz
Giải thích
Frequency = speed/wavelength = 1400m/s / 0.035m = 40000 Hz = 40 kHz