What is a wave?
A wave is a means of transferring energy from one place to another without a transfer of matter between the two points.
You can also use waves to transfer information
(Mobile phone ,radio)
What are mechanical waves?
Mechanical waves are vibrations that travel through a medium (a substance) sound waves, water waves, waves on springs and ropes and seismic waves produced by earthquakes
What are electromagnetic waves?
Electromagnetic waves can all travel through a vacuum at the speed of 30000 km/s. No medium is needed. Examples are light waves, radio waves and microwaves
What are transverse waves?
The direction of oscillation of a wave is perpendicular to the direction of motion of the wave. All EM waves are transverse waves.
What are longitudinal waves?
The direction of oscillation of a wave is parallel to the direction of motion of the wave
What is amplitude?
Distance from the rest position to the top of the wave measured in meters
What is wavelength?
Distance from one point on the wave to the identical point on the next wave measured in meters
What is time period?
The time for one wave to pass a given point or the time for one complete oscillation in seconds
What is frequency?
The number of waves or oscillations per second measured in hertz
What is the law of reflection?
The reflected waves move away from the barrier at an equal angle to the incident waves
The angle of incidence = the angle of refelction
How does a ripple tank work?
Ripple tanks allow us to produce waves and observe how they behave when we introduce barriers, different gaps and change how deep the water is
What happens to waves as they travel across a boundary between deep and shallow water?
Water travels faster in deep water than in shallow water. As the water gets shallower waves travel more slowly their wavelength decreases.
What is refraction?
Refraction occurs when a wave changes direction as it changes speed. When it passes from one medium to another. So the wavelength change as well but the frequency remain unchanged.
What is absorbtion?
What is transmission?
What is the human range of hearing?
20 - 20000 hz
What is ultrasound?
Ultrasound waves are longitudinal vibrations that have a frequency higher than the upper limit of human hearing 20000 Hz
What is an ultrasound scanner?
An ultrasound scanner is an electronic device which makes use of a transducer which can be placed on the surface through which it can send pulses of ultrasound waves which can then also be detected. The results can then be shown on a display screen
What are the uses of ultrasound scanners?
Ultrasound scanners are used for medical imaging to:
- look at organs inside the body
- look at damaged ligaments
-look at damaged muscles
- look at babies inside the womb
Can also be used for industrial purposes such as inspecting materials for defects and damage
Why can x-rays not be used to check the development of a baby in the womb?
X-rays cannot be used because of the ionising radiation which could harm the baby as the cells may mutate
What does ionising mean?
Ionising means it has enough energy to remove an electron from an atom forming an ion
Why is the fact that ultrasound is partially reflected by organ tissue useful?
The partial reflection of the waves at different tissues boundaries allows an image to be for,ed with the results
Why is the fact xrays pass through organ tissue not useful?
As the X-rays pass through the tissue the organs unaffected it would not be possible to form an image
How exactly do ultrasound scanners work?
- an ultrasound wave pulse from the transducer:
-Is partially reflected by different medium boundaries
-reflected waves return to the transducer with the time taken being monitored - as the reflected ultrasound waves are detected an image can be produced with the results for that point
- the transducer is then moved around the object to get a full image
