GCSE Science – GCSE Physics – Waves
KEY STAGE 4 – GCSE Physics Revision Guide – Waves for Detection and Exploration
Then use this Revision Guide to remember all the Key Points in the GCSE Syllabus and get Full Marks in your GCSE Physics Exam.
What is a wave?
‘Mechanical Waves’ can be described as:
a disturbance which travels through a medium (solid, liquid or gas) or
an oscillation in the particles of a particular medium which travels in a particular direction.
Examples of ‘waves’:
seismic waves (i.e. from earthquakes, explosions)
Different types of mechanical wave?
Longitudinal Waves: displacement (of particles) is parallel to the direction of the wave
NOTE: Longitudinal waves cannot travel through a vacuum!
Examples of Longitudinal Waves
Primary (faster) waves in earthquakes or explosions (can pass through solid and liquid mediums)
Transverse Waves: displacement of particles is perpendicular to the direction of the wave
NOTE: Transverse waves like light and electromagnetic waves can travel through a vacuum without slowing down!
Examples of Transverse Waves
Secondary (slower) waves in earthquakes or explosions (can only pass through a solid medium)
How can we use waves?
Remember: Animals like dolphins and bats use sound waves in a process called “echo-location”, to find their way around or find their food in the dark.
We can do the same:
Example of how we use sound waves and “sonar”:
Using ultrasonic waves above 20,000 Hertz or 20 ‘Kilohertz’ (above human audible range), we can measure distances between two materials of different densities.
A detector is placed close to the source of the waves
Waves are emitted from the source
Some of the waves will be ‘reflected’ back and ‘detected’
The time it took for the waves to ‘bounce’ back and be detected can be used to calculate the distance of the change in density/material
Calculate the distance: Multiply the speed of the wave/s by the time it took to bounce back!
Where is ‘echo-location’ or ‘sonar’ used by humans?
In ships and submarines to:
to find out the depth of the water
to look at the sea bed
to look for shoals of fish
to look for other submarines and ships.
As described above, in the same way as dolphins, pulses of sound waves are sent, bounce/reflect off an object (seabed, rock, or shoal of fish) and is detected upon their return.
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