Waves in air, fluids and solids：練習問題

A wave has a frequency of \(50\text{ Hz}\) and a wavelength of \(2.0\text{ m}\). What is the wave speed?

Which of the following statements correctly describes a longitudinal wave?

(HT only) When a sound wave enters the human ear, it causes the ear drum to vibrate. Which of the following is true regarding this process?

What is the frequency range of normal human hearing?

In the context of seismic waves, which statement correctly distinguishes between P-waves and S-waves?

A sound wave has a frequency of \( 500 \text{ Hz} \) and a wavelength of \( 0.66 \text{ m} \). Calculate the wave speed of this sound wave.

(HT only) Describe how the velocity of P-waves and S-waves changes when they encounter the boundary between the Earth's mantle and the liquid outer core, and explain what this reveals about the core's state.

(HT only) Ultrasound waves are used in both medical and industrial imaging to detect features hidden from direct observation. These waves are partially reflected at the boundary between different media.

a) A student uses an ultrasound probe to measure the thickness of a steel plate. The speed of ultrasound in steel is \(5900\text{ m/s}\). The time interval between the emission of the pulse and the detection of the reflected pulse from the back of the plate is \(1.2 \times 10^{-5}\text{ s}\). Calculate the thickness of the steel plate. [3 points]

b) Seismic waves are produced by earthquakes and are used to study the internal structure of the Earth. Explain how the properties of P-waves and S-waves provide evidence for the existence of a liquid outer core. [4 points]