P1 – Foundation part 4 Waves – Earthquakes and sounds

Sonar (ultrasound) We send out a pulse of ultrasound. It strikes something and is reflected. It arrives back at the detector. The time taken tells us how far away the object is.

Human hearing is 20Hz to 20,000Hz (or 20KHz). Sound below human hearing is called infrasound. Sound above human hearing is called ultrasound.

How will you be tested? Ultrasound from a fishing boat is used to find fish. (a) (i) Which of these is correct for ultrasound waves? Put a cross ( ) in the box next to your answer. (1) A ultrasound waves have a frequency above Hz B ultrasound waves have a frequency below 20 Hz C ultrasound waves have a wavelength above Hz D ultrasound waves have a wavelength below 20 Hz (ii) Complete the sentence by putting a cross ( ) in the box next to your answer. The system that uses ultrasound to find fish is called (1) A fibre optics B satellite transmission C sonar D thermal imaging

The diagram shows a fishing boat above some fish. Describe how ultrasound waves are used to detect the fish. You may add to the diagram to help with your answer. (2)

(a)(i ) A ultrasound waves have a frequency above Hz (a)(i i) C sonar (a)(i ii) a description including any two of the following:  (ultrasound waves / pulses) go down (through the water) (1)  (ultrasound waves are) reflected off fish (1)  (reflected ultrasound waves) are received by boat (1)  time delay (shows how deep fish are) (1) on diagram, wave or ray indicated as downwards idea of wave moving towards or hitting fish on diagram, waves or rays reflected off fish idea of wave bouncing off fish signal is timed ignore fish emitting ultrasound

Earthquakes Earthquakes happen when large parts of the Earth's crust and upper mantle move suddenly. Earthquakes produce shockwaves called seismic waves. These waves can be detected using seismographs.

P wavesS waves type of wavelongitudinaltransverse relative speedfasterslower can travel through solids and liquids solids only Both waves can be reflected and refracted.

Uneven heating from the core creates convection currents in the magma. This cause the tectonic plates to move. This is random so very hard to predict.

Measure the time difference between the arrival of the S and P waves. Three different seismometers are needed. The epicentre is where the lines cross and the earthquake happened.

How will you be tested? Earthquakes occur when two tectonic plates move against each other. Explain what causes the tectonic plates to move. You may draw a diagram if it helps your answer. (2)

Seismic (earthquake) waves can be either P- waves or S-waves. Which row of the table is correct for P-waves? Put a cross ( ) in the box next to your answer. (1) (b) Explain why it is difficult to predict when an earthquake will happen. (2)

Wave types (applies to a few topics)

ALL waves transfer energy. In transverse waves, the oscillations (vibrations) are at right angles to the direction of travel and energy transfer. Examples: S waves, all the EM spectrum, water waves.

In longitudinal waves, the oscillations are along the same direction as the direction of travel and energy transfer. Examples: sound waves, P waves.

LongitudinalVibrations in direction of travel. TransverseVibrations at 90 degrees to travel.

How will you be tested? (i) Sound is a longitudinal wave. State another example of a longitudinal wave. (1) (ii) Explain how a longitudinal wave is different from a transverse wave. You may draw a diagram to help with your answer. (2)

An earthquake emits P waves and S waves. (i) P waves are longitudinal waves. S waves are transverse waves. Explain the difference between longitudinal waves and transverse waves. (2) *(ii) Describe how scientists use P waves and S waves to locate the position of an underground earthquake. You may draw a labelled diagram to help with your answer. (6)

(i) P-wave / ultrasound / infrasound / shock (1) P/primary/pressure (wave) IGNORE slinky/spring/push- pull (ii)Any two from: vibrations different direction (1) In longitudinal (vibrations) move in same direction as wave/energy moves (1) In transverse (vibrations) move at right angles to direction wave/energy moves (1) In one is up and down, other is backwards and forwards / any two different motions in longitudinal (particles) move backwards and forwards in transverse (particles) move up and down/ side to side

(i)An explanation linking the following points recognising that directions of oscillation are different (1) comparison with correct detail for each wave (1) e.g. for longitudinal waves the oscillations are in the same direction as wave travels for transverse waves the oscillation are perpendicular to the direction in which the wave travels.

Basic statements the waves are detected by seismometers the waves travel at different speeds P waves travel faster than S waves two or more seismometers stations used Descriptions that include relationships between variables waves travelled same distance in different time distance travelled derived from speed and time two or more seismometers stations needed Full description description including the reasons for at least two seismometer stations a diagram explaining triangulation idea that difference in arrival time relates to how far the waves have travelled Ideas maybe expressed through a labelled diagram

11-2 description mentions appropriate detection instruments description mentions and different speeds or arrival times of waves the answer communicates ideas using simple language and uses limited scientific terminology spelling, punctuation and grammar are used with limited accuracy 23-4 description relates speed, distance and time description relates arrival time to speed the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately spelling, punctuation and grammar are used with some accuracy description including some correct spatial relationships description including the need for data from more than one location the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately spelling, punctuation and grammar are used with few errors