Physics A Flashcards
Amplitude
Height of a wave from its undisturbed position
Wavelength
The distance between two crests or two troughs
Frequency
Number of waves passing through a point each second
Longitudinal
Oscillations are along the same direction as the direction of travel
eg sound waves
Transverse
Oscillations are at right angles to the direction of travel
eg water waves, all EM waves
Period
Time needed for one wave to pass a given point
Compression
Region in a longitudinal wave where the particles are closest together.
Rarefaction
Region in a longitudinal wave where the particles are furthest apart
Absorb
When the energy of an EM wave is taken up by an object
Transmit
When a wave is able to pass through a material
Reflect
The wave bounces of a surface; the angle of incidence is equal to the angle of reflection
Refract
The wave changes direction when it enters a medium of different density where it has a different speed
Radio waves
Uses : television , radio
Why : reflected by ionosphere so can travel over long distances
Microwaves
Uses : satellite communications cooking food
Why : able to pass through atmosphere to satellites
Has heating effect
Infrared
Uses : cooking food, electrical heaters infrared cameras.
Why : has a heating effect, is emitted by objects so can be detected
Visible light
Uses : fibre optic communications
Why : able to pass along a cable by total internal reflection
Ultra violet
Uses : sun tanning , energy efficient lamps
Why : increases amount of melanin (brown pigment) in skin
Risk : premature skin ageing , increase risk of skin cancer (some can ionise)
X-rays
Uses : medical imaging, treatments
Why : absorbed by bone but transmitted through soft tissue
Risk : ionising can cause skin mutation of genes, cancer
Gamma rays
Uses : medical imaging, treatments
Why : able to be passed out the icy and detected by gamma cameras, can kill cancerous cells
Risk : Ionising - can cause mutation of genes and cancer
Ionising
High energy radiation which can remove electrons leaving ions. If this happens in DNA it can cause a mutation that could lead to cancer.
EM spectrum
The collective name for all types of EM radiation. They are all transverse waves that all travel at 300,000,000 m/s
Production
Gamma rays are produce from the decay of an unstable nucleus
Radio waves are produced by oscillations in electrical circuits
