SoundEdexcel GCSE Physics: Flashcards

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How does the ear convert sound waves into something the body can detect?

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How does the ear convert sound waves into something the body can detect?: Sound waves in air make the eardrum vibrate, which passes vibrations through bones in the middle ear; this conversion process only works over a limited frequency range.
Define ultrasound.: Sound with a frequency greater than 20 000 Hz.
Define infrasound.: Sound with a frequency less than 20 Hz.
What is sonar and how does it work?: A technique that uses reflected ultrasound pulses to find distance underwater; the time for the pulse to travel there and back, combined with the wave speed, gives the distance.
How is ultrasound used in foetal scanning?: Ultrasound is directed into the body and reflects differently off different tissue boundaries; these reflections are used to build an image, without the risks of ionising radiation.
How is infrasound used to explore the Earth's core?: Infrasound and seismic waves travel through and reflect off boundaries inside the Earth; scientists use their travel times to work out the structure of the Earth's interior.
When sound travels from air into a denser medium, what stays the same?: The frequency stays the same — only the wave's velocity and wavelength change.
When a sound wave speeds up crossing into a new medium, what happens to its wavelength?: The wavelength increases, because v = f × λ and frequency stays constant.
In the core practical, how would you measure the wavelength of a standing wave on a solid (e.g. a string)?: Measure the distance between nodes with a ruler, since the wave pattern stays in a fixed position.
In the core practical, how would you measure the speed of sound in air (a fluid)?: Time how long the sound takes to travel a known distance using a stopwatch, then calculate v = x/t.
Why should you repeat readings and average them in the core practical?: To reduce the effect of random error and get a more reliable value for the wave speed.
Give the equation used to calculate depth using an ultrasound echo.: Depth = (wave speed × total time) ÷ 2, since the wave travels down to the reflecting surface and back up again.