3.4 Sound EXT

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3.4 Sound EXT

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3.4a The big picture

1) Which travels fastest – the sound of thunder or the light of the flash of lightning?

1 point

2) Which of these shows the relationship between speed, distance and time?

1 point

𝑡𝑖𝑚𝑒 = 𝑠𝑝𝑒𝑒𝑑 × 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒

𝑠𝑝𝑒𝑒𝑑 = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 × 𝑡𝑖𝑚𝑒

𝑠𝑝𝑒𝑒𝑑 = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 ÷ 𝑡𝑖𝑚𝑒

𝑠𝑝𝑒𝑒𝑑 = 𝑡𝑖𝑚𝑒 ÷ 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒

Clear selection

3) If the sound of thunder takes 5.0 seconds to reach you and it travels at 333m/s, approximately how far away was the lightning strike?

1 point

1.5km

1.6km

1.7km

3.3km

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3.4b Describing sound waves

1) What will happen to the sound we hear if the amplitude and frequency of the sound wave is decreased?

1 point

The sound will become louder and lower pitched.

The sound will become louder and higher pitched.

The sound will become quieter and lower pitched.

The sound will become quieter and higher pitched.

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2) What is an echo?

1 point

The reflection of a light wave from a shiny surface.

The reflection of a sound wave from a hard surface.

The refraction of a sound wave at a boundary.

The increase in pressure caused by a sound wave passing a point.

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3) i) As a sound wave travels through a medium it produces moving regions where the molecules are closer together than normal called ………………… and …

1 point

3) ii) … regions where the molecules are further apart than normal, known as ………………… .

1 point

3.4c Using an oscilloscope to visualise sound waves

1) The figure shows four wave traces produced on an oscilloscope. Which trace is produced by the loudest sound?

1 point

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2) The figure shows four wave traces produced on an oscilloscope. Which trace is produced by the highest frequency sound?

1 point

Clear selection

3) The figure shows four wave traces produced on an oscilloscope. Which trace is produced by the lowest pitch sound?

1 point

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4) i) The higher the ………………… of the sound the closer together the wave peaks appear.

1 point

4) ii) The louder the sound, the ………………… the waves appear on the screen.

1 point

3.4d The speed of sound

1) A student sees a flash of lightning strike a tower they know is 2.50km away. They hear the thunder 7.40 seconds later. Use this data to estimate the speed of sound in air.

1 point

2.96 m/s

33.0 m/s

338 m/s

350 m/s

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2) Why can sound waves not travel in a vacuum?

1 point

There are no particles.

Sound waves are reflected by the particles in a vacuum.

The forces between the particles are too great.

The particles are too close together.

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4) i) Sound cannot travel through a ………………… (empty space) as …

1 point

4) ii) … there are no ………………… to transfer the vibrations.

1 point

3.4e Measuring the speed of sound

1) A student times how long it takes for a sound wave to travel 150m across a field. What is the best estimate of the speed of sound according to the data? Their timings are shown in the table:

1 point

320 m/s

330 m/s

335 m/s

340 m/s

Clear selection

2) A student measured the time it took for a sound wave to travel 100m using a stopwatch. They found that the speed was 200m/s. The true value is 340m/s.

Which of the following is the most likely cause for the difference in values?

1 point

The student's reaction time was too slow.

The student's reaction time was too fast.

The stopwatch had too high a resolution.

The wind causes a change in the speed of sound.

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3) A stopwatch measures time to the nearest 0.1s.

Why is this unsuitable for measuring the speed of sound over a distance of 100m?

1 point

The precision of the measurement would be too low.

The precision of the measurement would be too high.

The stopwatch has a zero error.

The distance is too long.

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4) True or false? The speed of sound in air is always 333m/s.

1 point

3.4f Ultrasound

1) Above what frequency is a sound wave classed as ultrasound?

1 point

20 Hz

200 Hz

2000 Hz

20 000 Hz

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2) An ultrasound pulse is used to measure the thickness of a layer of skin.

The pulse is transmitted through the skin and the echo from the back surface arrives 5.2×10⁻⁷ seconds later.

If the speed of sound in the skin is 1730m/s, what is the thickness of the skin?

1 point

4.5×10⁻⁷m

4.5×10⁻⁴m

9.0×10⁻⁴m

0.45m

Clear selection

3) True or false? Ultrasound causes ionisation.

1 point

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