Sound (Edexcel GCSE Physics): Flashcards
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- FrontSound Waves
Define echo.
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Cards in this collection (22)
Define echo.
An echo is a sound wave that is reflected from the surface of a solid.
What happens to the energy of a sound wave when it meets a solid surface?
Some of the energy is reflected, some is transmitted through the solid, and some is absorbed by the solid.
Why is sound described as a pressure wave?
Sound consists of compressions and rarefactions, which cause pressure to vary in time with the wave.
Define natural frequency.
The natural frequency of an object is the frequency at which it tends to vibrate.
Sound waves with a frequency close to a solid's natural frequency cause ______ vibrations than sound waves with frequencies much larger or smaller.
Sound waves with a frequency close to a solid's natural frequency cause larger vibrations than sound waves with frequencies much larger or smaller.
Which two solid components transfer sound vibrations within the human ear?
The eardrum and three small bones.
How does the cochlea produce the sensation of sound?
Tiny hairs inside the cochlea detect vibrations in the liquid and create electrical impulses, which travel along neurones in the auditory nerve to the brain.
True or False?
The human ear can detect sound waves of any frequency.
False.
The ear only transfers sound efficiently over a limited range, so humans can only hear between 20 Hz and 20 000 Hz.
Define ultrasound.
Ultrasound is a sound wave with a frequency above 20 000 Hz, above the human hearing range.
Define infrasound.
Infrasound is a sound wave with a frequency below 20 Hz, below the human hearing range.
How is sonar used to determine the depth of the ocean?
Ultrasound is reflected off the ocean floor. The time taken for the wave to return is used to calculate depth, since the distance travelled is twice the depth of the water.
How does an ultrasound scanner produce an image of a foetus?
A transducer produces ultrasound waves that reflect at boundaries between tissues. The reflected echoes generate electrical signals, which are used with the wave speed and echo time to calculate distances and build an image.
Which type of seismic wave is classed as infrasound, and why?
P-waves, because they are very low frequency sound waves below 20 Hz.
P-waves are ______ waves, while S-waves are ______ waves.
P-waves are longitudinal waves, while S-waves are transverse waves.
True or False?
S-waves can travel through the Earth's liquid outer core.
False.
S-waves are transverse and can only travel through solids, so they cannot pass through the liquid outer core.
What do seismic waves reveal about the structure of the Earth's core?
Only P-waves are detected on the opposite side of the Earth to an earthquake, showing the outer core is liquid. Shadow zones with no P-waves show the inner core is solid.
Why do sound waves travel fastest in solids and slowest in gases?
In solids, molecules are closest together, so energy transfers faster between them. In gases, molecules are furthest apart, so energy transfers slowest.
Define refraction (of a sound wave).
Refraction is a change in direction of a sound wave, caused by a change in its speed as it moves between media.
Which two properties of a sound wave change when it moves from one medium to another?
Its wave speed and wavelength.
Why does sound travel further at night than during the day?
At night, the air near the ground is cooler and denser, so sound travels faster near the ground and refracts towards the ground, allowing it to travel further.
True or False?
Sound waves travel faster in warm air than in cold air.
True.
This causes sound to refract towards the sky during the day, as the wave speeds up moving into the warmer air above.
During the day, sound refracts towards the ______, while at night it refracts towards the ______.
During the day, sound refracts towards the sky, while at night it refracts towards the ground.
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