Combined Physics - 6.6 Flashcards
What two types of wave are there?
Transverse or longitudinal
Give an example of a transverse wave
- All electromagnetic waves
- A ripple on water
- A wave on a string
Give an example of a longitudinal wave
- Sound waves in air
- Ultrasound
- Shock waves (e.g. some seismic waves)
What vibrations do transverse waves have?
Perpendicular (the oscillations are perpendicular to the direction of energy transfer)
What vibrations do longitudinal waves have?
Parallel (the oscillations are parallel to the direction of energy transfer)
What do longitudinal waves show areas of?
Compression and rarefaction
What are waves?
Transfers of energy (the particles remain in the same place)
Describe the wave feature: amplitude
The maximum displacement of a point on the wave from its undisturbed position
Describe the wave feature: wavelength
The distance between the same point on two adjacent waves
Describe the wave feature: frequency
The number of complete waves passing a certain point in a second (1 Hz is 1 wave per second)
Describe the wave feature: period
The amount of time taken for a full cycle of the wave
What is wave speed?
The speed at which the energy is transferred (or the wave moves) through a medium
What is the wave equation all waves obey?
Describe electromagnetic waves
Transverse waves which transfer energy from the source of the waves to an absorber
What do electromagnetic waves form?
A continuous spectrum
What velocity do electromagnetic waves travel at through a vacuum?
The same velocity
List the waves of the electromagnetic spectrum in order of wavelength and frequency
What EM waves can our eyes detect?
Visible light (only a limited range of the EM spectrum can be detected)
Higher Q. When wavelength varies, different substances may do what?
Absorb, transmit, refract or reflect the EM waves differently
Higher Q. What causes some effects, such as refraction?
The difference in velocity of a wave at the boundary between two different media
Higher Q. What can oscillations in electrical circuits cause?
Radio waves
Higher Q. How can radio waves themselves induce oscillations in an electrical circuit?
Radio waves can be absorbed, creating an alternating current with the same frequency as the radio wave itself
What can cause EM waves being generated or absorbed over a wide frequency range?
Changes in atoms and the nuclei of atoms
Where do gamma rays originate from?
Changes in the nucleus of an atom
What EM waves can have hazardous effects on human body tissue?
Ultraviolet waves, X-rays and gamma rays
What is a measure of the risk of harm resulting from an exposure of the body to radiation?
Radiation dose (sieverts (Sv))
How may millisieverts (mSv) are in one sievert (Sv)?
1000 millisieverts (mSv) = 1 sievert (Sv)
What danger does ultraviolet light pose?
Skin can age prematurely and increase the risk to skin cancers
What danger do X-rays and gamma rays pose?
They are ionising radiation: mutations of genes and cancers
What practical applications are there for radio waves?
Television and radio
What practical applications are there for microwaves?
Satellite communications and cooking food
What practical applications are there for infrared waves?
Electrical heaters, cooking food and infrared cameras
What practical applications are there for visible light?
Fibre optics
What practical applications are there for ultraviolet light?
Energy efficient lamps and sun-tanning
What practical applications are there for X-rays and gamma rays?
Medical imaging and treatments
