Sound Waves (physics Only) (ht Only) (GCSE Physics)

A moving listener hears frequency f` from a stationary source frequency f due to the Doppler effect. If the listener moves toward the source at speed v_l (<< speed of sound c), which approximate relation applies?

An ultrasound pulse (1 MHz) is emitted into tissue where speed is 1540 m/s. What is the pulse wavelength in tissue?

A student measures a sound level of 60 dB and another of 90 dB. How many times larger is the intensity (power per unit area) of the 90 dB sound compared with the 60 dB sound? (Use 10 log10 rule.)

A heavy gas (molecular weight higher than air) at the same temperature affects speed of sound. For identical temperature, which statement is true about speed of sound c = sqrt(?RT/M)?

A sound source emits power P uniformly in all directions. At a distance r the intensity I = P / (4pr^2). If the distance is doubled, how does I change?

A closed–open tube of length L resonates at f1 (fundamental). Which harmonic series is produced?

An open pipe supports a standing wave with first overtone (second harmonic) at frequency 600 Hz. What is the fundamental frequency?

Two pure tones of frequencies 400 Hz and 406 Hz are played together. What is the beat frequency (the frequency of amplitude modulation heard)?

A student measures the minimum audible level at a frequency and finds 20 arbitrary units for a young person and 60 units for an older person. Which physical effect could explain the older person’s raised threshold at high frequencies?

A student measures phase difference between two coherent sources and finds 180° (p radians). What kind of interference will occur at a point equidistant from the sources?

A moving-coil loudspeaker uses alternating current in a coil placed in a permanent magnetic field. Which property of the output sound is changed by increasing the amplitude of the alternating current (keeping frequency constant)?