Waves for detection & exploration

This question is about both infrasound and ultrasound.

Which of these is a frequency of infrasound ?

Figure 1 shows a technician standing in front of a wall.

The technician has a device that can emit and detect ultrasound.

The device emits a pulse of ultrasound towards the wall and detects the echo of the pulse a short time later.

The wall is 7.6 m from the device.

The speed of ultrasound in air is 330 m / s.

Calculate the time between the emission of the pulse and the detection of the echo.

Explain why humans cannot hear infrasound.

Which row of the table shows two transverse waves?

Figure 16 is an energy diagram for a sound wave incident on a sound-insulating board.

sound-insulating

The incident energy is 0.25 J.

The absorbed energy is 67 % of the incident energy.

The reflected energy is 15 % of the incident energy.

Calculate the amount of the transmitted energy.

Give one way to reduce the percentage of energy transmitted through the sound-insulating board.

The ratio of the absorbed energy E_a to incident energy E_i is the coefficient of absorption of sound α.

The table in Figure 17 gives the coefficient of absorption for various materials.

Explain why rooms with carpets and curtains are less noisy than rooms without them.

Use the information given in Figure 17 in your answer.

* (d) Explain how sound waves can be used to determine the depth of the ocean directly underneath a boat.

You may draw a diagram to help with your answer.

Figure 1 shows a bat and its prey.

The bat emits a high frequency sound pulse to locate its prey.

The speed of sound in air is 330 m / s.

The wavelength of the sound is 11 mm.

Calculate the frequency of the sound.

Use the equation

v = f × λ

The pulse returns to the bat after a time of 18 ms.

Calculate the distance from the bat to its prey.

The human ear can only detect frequencies below ultrasound and above infrasound.

Which of these gives the approximate range of frequencies for the human ear?

Suggest two reasons why there are limits to the frequencies that a human ear can detect.

Ultrasound can be used to find cracks in metals.

Figure 13a shows the signals emitted and received when the metal bar has no cracks.

Figure 13b shows the signals emitted and received when the metal bar has a crack.

Explain how the signals in Figure 13a and Figure 13b show that there is a crack in the metal bar in Figure 13b.

Suggest one reason why the amplitude of signal R in Figure 13b is smaller than the amplitude of signal P shown in Figure 13a.

This question is about ultrasound.

Which of these is a frequency of ultrasound?

Ultrasound has many uses.

One device called a pest repeller emits ultrasound.

The ultrasound keeps mice out of the garden.

Explain why the device affects mice but does not affect humans.

A technician has a different ultrasound device.

This device can emit and detect short pulses of ultrasound.

The device can also measure the time, in ms, from emitting a pulse to detecting the same pulse.

Describe how the technician can use this device to determine the speed of ultrasound in air.

Figure 14 shows the hearing responses of a human, a mouse and a bird over a range of frequencies of sound.

.25.5 1 2 4 8 16 32 64 128

Describe two differences between the hearing responses of the human and the mouse.

A farmer wants to use an alarm to scare away these birds.

State which frequency would be most effective. Give the appropriate units.

State the reason for your choice of frequency in (ii).

Describe the difference between ‘infrasound’ and ‘ultrasound’.

A transducer can transmit and detect ultrasonic waves.

Figure 15 shows ultrasonic waves transmitted by the transducer on the bottom of

The waves reflect off the sea floor and are received back at the transducer.

The waves travel at 1500 m / s.

The time between transmission and reception is 48 milliseconds.

Calculate the depth of water, D, shown in Figure 15.

depth of water, D =_........

Explain how vibrations from earthquakes may be used to study the core of the Earth.

Sonar is an example of a use of ultrasound.

State one other example of a use of ultrasound.

State an example of a use of infrasound.

Figure 1 shows the depth of the sea, measured using sonar, at different distances from the shore.

A technician on a boat uses sonar pulses to measure the depth of the sea when the boat is 120 m from the shore.

Calculate the total time of travel for the sonar pulse used to make this measurement.

The speed of the sonar pulse in seawater is 1600 m/s.