Waves in Air, Fluids & Solids Practice Questions

Ripples on a water surface are transverse waves.

Describe what is meant by a transverse wave.

As the ripples pass, the leaf bobs up and down but stays in the same place on the water surface.

Explain how the movement of the leaf is evidence that it is the wave, and not the water, that travels across the pond.

Sound waves travelling through air are longitudinal.

Name the two types of region found in a longitudinal wave.

Use Figure 1 to determine the amplitude of the wave.

Amplitude = .............................. cm

Use Figure 1 to determine the wavelength of the wave.

Wavelength = .............................. cm

The frequency of the wave is $5\ \text{Hz}$.

Calculate the speed of the wave.

Give your answer in m/s.

State the range of frequencies of normal human hearing.

Describe how a sound wave travelling through air causes the sensation of sound in the ear.

A dog whistle produces a sound of frequency $30\ \text{kHz}$. A person cannot hear the whistle.

Explain why.

Calculate the wavelength of the sound wave in air.

Calculate the period of the sound wave.

Give your answer in seconds.

Describe how the student could measure the wavelength of the ripples in the tank.

The bar vibrated at a frequency of $12\ \text{Hz}$.

The student measured the distance across 6 wavelengths as $9.0\ \text{cm}$.

Calculate the speed of the ripples in m/s.

Explain why measuring the distance across 6 wavelengths gives a more accurate value for the wavelength than measuring a single wavelength.

Calculate the speed of sound in air obtained from this measurement.

Another student suggested measuring the time using two people, one with a stopwatch, standing at each microphone position.

Explain why this method would give a much less accurate value for the speed of sound.

Explain why moving the microphones further apart would improve the accuracy of the result.

State what is meant by ultrasound and give one use of ultrasound in industry.

An ultrasound machine produces waves of frequency $2.5\ \text{MHz}$.

The speed of these waves in soft tissue is $1540\ \text{m/s}$.

Calculate the wavelength of the ultrasound waves in soft tissue.

A pulse of ultrasound is sent into the body. It is partially reflected at a boundary between two types of tissue. The reflected pulse is detected $1.2 \times 10^{-4}\ \text{s}$ after the pulse was sent.

Calculate the depth of the boundary below the skin.

At the first position of the ship, the echo from the seabed is detected $0.36\ \text{s}$ after the pulse is sent out.

Calculate the depth of the water at this position.

The ship moves to a second position. Here the echo from the seabed is detected $0.50\ \text{s}$ after the pulse is sent out.

Calculate how much deeper the water is at the second position.

At the second position, a second, weaker echo is detected a short time after the echo from the seabed.

Explain why a second echo is detected.

On Figure 2, draw the normal at P and draw the reflected ray.

State the angle of reflection, measured from the normal.

Angle of reflection = .............................. °

The student marked the position of each ray with two crosses. Explain why the two crosses should be placed as far apart as possible.

The student replaced the mirror with a sheet of matt black card. No reflected ray could be seen.

Explain what happens to the light at the surface of the black card.

Use Figure 3 to determine the period of the sound wave.

Give your answer in milliseconds.

Period = .............................. ms

Calculate the frequency of the sound wave.

Calculate the wavelength of this sound wave in air.

speed of sound in air $= 340\ \text{m/s}$

The loudspeaker is adjusted so that the note becomes louder, but its pitch does not change.

Describe how the trace on the oscilloscope changes.

Calculate the wavelength of this sound in air.

The sound then travels from the air into the water. Its frequency does not change.

Calculate the wavelength of the sound in the water and, by comparing your two answers, describe how the wavelength changes as the sound enters the water.

Explain why the frequency of the sound does not change when the wave passes from the air into the water.

A seismometer $2000\ \text{km}$ from an earthquake detects the P-waves before it detects the S-waves.

Explain why.

Explain how the study of P-waves and S-waves has provided evidence for the structure and size of the Earth's core.

Calculate the mean time and use it to calculate the speed of the wave pulse.

Estimate the percentage uncertainty in the mean time.

Show clearly how you obtain your estimate.

Suggest one change the student could make to the apparatus or method that would reduce the uncertainty in the measured speed, and explain why it would help.