M. RahmanP1 TOPIC 4

1) Ultrasound is ……..a) Longitudinal waves below 20 Hzb) Longitudinal waves above 20,000 Hzc) Transverse waves above 20,000 Hz

Answer. a) Longitudinal waves above 20,000 Hz

M. RahmanP1 TOPIC 4

2) Human hearing range is;a) Above 20,000 Hzb) Below 20 Hzc) Between 20-20,000 Hz

Answerc) Between 20-20,000 Hz

M. RahmanP1 TOPIC 4

3) How is ultrasound used for in foetal scanning?

Answer• Ultrasound waves pass through the body;• at boundaries between two different

media;• some waves are reflected back • and detected to produce a computer

image

M. RahmanP1 TOPIC 4

4)How is Sonar used in boats and submarines to detect stuff in water?Answer• Boats and submarines emit ultrasound,• which is reflected off the object (ie

boats, sea bed, marine animals)• The time-delay between emitting and

detecting the waves is used to calculate how far the other object is using

• S=d/t

M. RahmanP1 TOPIC 4

5) Calculation: A pulse of ultrasound takes 5 seconds to travel from a boat to a ship wreck under the sea and back again. How far away is the shipwreck? (speed of sound in water = 1520 m/s)

Answer• Speed = distance/time• rearrange, distance = speed x time• = 1520 x 5 = 7200 m• Its 5s there and back so the ship wreck is only

half the distance away so divide by 2.• = 7200/2 = 3600 m

M. RahmanP1 TOPIC 4

6) Infrasound is ……..a) Longitudinal waves below 20 Hzb) Longitudinal waves above 20 Hzc) Transverse waves above 20,000 Hz

Answera) Longitudinal waves below 20

Hz

M. RahmanP1 TOPIC 4

7) Explain how animals use infrasound?

Answer.• Elephants use infrasound to

communicate with other members of their heard over long distances.• Tigers use infrasound in the

growls and roars which can be heard by rivals or mates

M. RahmanP1 TOPIC 4

8) Why can some volcanic eruptions be detected at a distance? Answer• Infrasound is long wavelength,• that means they can travel long

distances and diffract around objects.

M. RahmanP1 TOPIC 4

9) Which of these statements are false?1. Low frequency, long wavelength sounds travel further.2. Larger animals (elephant) make higher frequency sounds compared

to little ones (mice).3. Volcanic eruptions make high frequency sounds that can be heard

from a long distance.

AnswerFalse statements are:

2. Larger animals (elephant) make higher frequency sounds compared to little ones (mice). 3. Volcanic eruptions make high frequency sounds that can be heard from a long distance

M. RahmanP1 TOPIC 4

10) Which of the following statements are false?1. Sounds travel further in air then in water.2. Whales can communicate over larger distances than elephants can.3. Animals that can use infrasound can communicate further distances than animals that use higher frequencies.

Answer.False statements are:1. Sounds travel further in air then in water.

M. RahmanP1 TOPIC 4

11) The structure of the earth from inside out are:a) Crust, mantle, outer core; inner coreb) outer core; mantle; inner core; crustc) Inner core; outer core; mantle; crust

Answer.c) Inner core; outer core; mantle; crust

M. RahmanP1 TOPIC 4

12) What is the inner core and outer made from?

Answer.Inner core –solidOuter core -liquid

M. RahmanP1 TOPIC 4

13) What is the mantle made from?

Answer• Molten rock• Heat is produced, causing

convection currents.

M. RahmanP1 TOPIC 4

14) Explain how heat from the mantle causes earth quakes? (3)

Answera) Heat from the mantle produce convection

currents;b) causing the plates to movec) At plate boundaries, plates may rub against

each other,d) causing pressure to build up.e) Sudden release of pressure as a result of the

plates sliding past each other causes an earth quake.

M. RahmanP1 TOPIC 4

15) Why is it difficult to predict an earth quake? (3)

Answer• Earthquakes are totally random – • although there are areas where they are

more likely to happen than others (near fault lines).

• The fault line has a build up of stresses and any part of that fault line could snap out of line at any moment.

M. RahmanP1 TOPIC 4

16). Give two ways seismic waves are created

Answer.• Earthquakes• Explosions

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17). What instrument is used to detect seismic waves created from an earth quake?

Answer• Seismometer.

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18) What are the two types of seismic waves?

Answer.P wavesS waves

M. RahmanP1 TOPIC 4

19) What are the properties of P-waves? (4)Answer.• These are Push-Pull waves• They are longitudinal• They can travel through liquid and solid so

they can travel through the earth’s core.• They travel fast.• They are bent by the changing density of

the rock. • They are bent sharply when the material

changes suddenly.

M. RahmanP1 TOPIC 4

20) What are the properties of S-waves ?(4)

Answer.• They are Side to Side waves.• They are transverse• They can only travel through solids.• They are slower than P-waves.• They are bent by the changing density of

the rock. • They are bent sharply when the material

changes suddenly

M. RahmanP1 TOPIC 4

21) What happens when seismic waves reach a boundary between different layers of the earth?

Answer.• They are reflected and • refracted

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22) What is the phenomenon called which causes the waves to change speed and direction?a) Reflectionb) Refractionc) Diffraction

Answer.

b) Refraction

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23) Why does the speed and direction (refraction) of the seismic wave change?

AnswerWhen there is a change in density-between different layers of material.ie between mantle and the outer core?

M. RahmanP1 TOPIC 4

24) When there is a gradual change in speed a curved path is made by the wave, what happens when there is a sudden change in properties/densities between layers?

Answer• The wave speed changes

abruptly and• and the path has a kink

M. RahmanP1 TOPIC 4

25) Which waves are detected first by a seismometer travelling from the epicentre of an earth quake.A) P-wavesB) S-waves

Answer A) P-waves-they travel the fastest.

M. RahmanP1 TOPIC 4

26) What does arrival time mean?

AnswerThe time taken for a wave (P-wave or S-wave) to travel from the epicentre of the earth quake to the seismometer?

M. RahmanP1 TOPIC 4

Describe how scientists use P waves and S waves to locate the position of

an underground earthquake (6).• Seismic waves are detected by seisometers• You need at least 3 seisometers• The arrival time of s waves will be slower then p

waves.• The further the seisometer is away from earth quake

the greater the difference between the arrival times.• Distance can be worked out because the arrival time

is known• A circle is drawn to indicate the distance • The point at which three circles meet is called the

epicentre