Topic 6-Waves Flashcards
What do waves do?
Waves transfer energy
What is the wavelength?
Distance between the same points on two consecutive waves
Peak to peak/trough to trough
What is amplitude?
Distance from the equilibrium line to the maximum displacement (crest or trough)
What is frequency?
The number of waves that pass a single point per second
What is the wave period?
The time taken for a whole wave to completely pass a single point
What is frequency measured in?
Hertz (Hz)
What are transverse waves?
Have peaks and troughs
Vibrations are at right angles to the direction of travel
Eg light, seismic s-waves, electromagnetic waves
What are longitudinal waves?
A wave for which the oscillations are parallel to the direction of energy
Has compressions and rarefactions
Eg sound waves, seismic p-waves
What are the two parts of a longitudinal wave called
Compressions and rarefactions
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compression
What word is used to describe when a wave bounces off a surface?
Reflection
How do sound waves travel through a solid?
The particles in the solid vibrate and transfer kinetic energy through the material
What is the frequency range of human hearing?
20Hz-20,000Hz
What are ultrasound waves?
Waves that have a frequency higher than the upper limit of human hearing
Give an example use for ultrasound waves
Medical imaging
Industrial imaging
Describe how medical imaging uses ultrasound waves
Transducer is placed on the body and detects sets of ultrasound waves
Each ultrasound wave pulse is partially reflected from the different tissue boundaries in its path
It then returns to the transducer as a sequence of waves
What are some advantages of using ultrasound waves in medical imaging?
It can be used to scan organs and other soft tissues
Non ionising meaning it does not have enough energy to remove an electron to ionise and atom, meaning it is harmless
What natural event causes seismic waves to be produced? What types are produced?
Earth quakes
They produce both P-waves and S-waves
Describe how industrial imaging uses ultrasound waves
Flaws in the metal castings can be detected using ultrasound waves
A flaw might be an internal crack, which creates a boundary inside the metal
Waves are partly reflected from this boundary
Waves are detected by transducer and displayed on an oscilloscope screen/computer monitor
State a difference between the mediums that P-waves and S-waves can travel through
P-waves travel through both solids and liquids
S-waves only travel through solids (not liquids)
What technique is used to detect objects in deep water and measure water depth?
Echo sounding
High frequency sound waves are emitted reflected and detected
Time difference between emission and detection alongside wave speed, are used to calculate distances
There is no air in space
Astronauts in space cannot hear sounds from outside their spacesuits
Explain this
Sound cannot travel through free space because there are no particles to vibrate
The frequency of an ultrasound wave used in a hospital is 2x10^6
It is not possible to produce ultrasound waves of this frequency using a tuning fork
Explain why
Frequency is very high so tuning fork would be very small
What is an ultrasound?
It cannot be heard by humans
Above 20,000 hZ
Ultrasound is used for pre-natal scanning. This is much safer that using X-rays. However, doctors were only sure ultrasound was safe after experiments of mice
Do you think the ultrasound experiments on mice were justified?
They were justified because ultrasound has been proved useful in medical and industrial processes
Unethical to experiment on humans so it is better to experiment of animals
Explain what scientists should do if they find evidence that ultrasound may be harmful to human health?
Carry out more research to check reliability
Describe the features of an x-ray is and what happens to this type of wave after it has entered the body
X-rays are electromagnetic waves that have a high frequency and high energy.
They have a short wavelength
When they enter the body they are absorbed by the bone
Describe the features of ultrasounds and what happens to this type of wave after it has entered the body
Frequency above 20,000 Hz
Longitudinal
Beyond the human limit of hearing
Partially reflected at a boundary between two different medias
Travel at different speeds through different media
Give uses of ultrasounds for medical treatments
Removing plaque from teeth
Removal of kidney stones
Repair of damaged tissue
Describe the differences between longitudinal waves and transverse waves
The oscillation/vibration causing the wave for a transverse wave is perpendicular to the direction of travel
For a longitudinal wave, it is parallel to the direction of energy transfer
Advantage of CT scanning
Easier to see a problem
Images have high resolution
Disadvantage of CT scanning
X-ray scans are ionising
Mutates cells
Explain how ultrasonic waves are used the image of an unborn baby
The waves are partially reflected when they hit a boundary between two medias
Time takes for reflected wave to return in used to produce image
The diagram shows an ultrasound transmitter and detector fixed to the front of a metal block. The block has an internal crack
The diagram below shows the screen of the oscilloscope connected to the detector
Explain why pulse A and pulse B occur
Transmitted waves are partially reflected at boundary
Pulse A indicated the crack
Pulse B indicated the back of the crack
What happens to the ultrasound which reaches the boundary between two different media and is not reflected?
It is absorbed and is transmitted/changes speed
