Waves SAEED Flashcards
Define what a wave is in physics
A wave is the transfer of energy without the transfer of matter
What is the differences between longitudinal waves and transverse waves?
The direction of the oscillations
Longitudinal - parallel
Transverse - perpendicular
Which direction do the longitudinal waves have?
The vibrations are parallel to the direction of wave travel
Which direction do the transverse waves have?
The vibrations are at right angles to the direction of wave travel.
Information about mechanical waves….
Mechanical waves cause oscillations of particles in a solid, liquid or gas and must have a medium to travel through
Information about electromagnetic waves….
Electromagnetic waves cause oscillations in electrical and magnetic fields
What does the “rest position” in a wave show?
The undisturbed position of particles or fields when they are not vibrating
What does the “displacement” in a wave show?
The distance that a certain point in the medium has moved from its rest position
What does the “peak” in a wave show?
The highest point above the rest position
What does the “trough” in a wave show?
The lowest point below the rest position
What does “amplitude” mean in terms of waves?
The maximum displacement of a point of a wave from its rest position
What does “wavelength” mean in terms of waves?
Distance covered by a full cycle of the wave, usually measured from peak to peak, or trough to trough
What does “time period” mean in terms of waves?
The time taken for a full cycle of the wave, usually measured from peak to peak, or trough to trough
What does “frequency” mean in terms of waves?
The number of waves passing a point each second
What are electromagnetic waves?
Are oscillating electric and magnetic fields that progress through space without the need for a substance
The vibrating electric field generates a vibrating magnetic field further away and so on
Examples of electromagnetic waves
Radio waves Microwaves Infrared radiation Light Ultraviolet radiation X - rays Gamma radiation
Examples of longitudinal waves
Sound waves
Primary seismic waves
Compression waves on a slinky toy
How do you send longituinal waves along a slinky?
When one end of the slinky is moved to and fro repeatedly, each “forward” movement causes a compression wave to pass along the slinky as the coils push into each other. Each “reverse” movement causes the coils to move apart so rarefaction (expansion) wave passes along the slinky
Examples of transverse waves
Electromagnetic waves
Secondary seismic waves
Waves on a string or a wire
How do transverse waves travel along a rope?
When one end of the rope is moved from side to side repeatedly, these sideways movements travel along the rope, as each unaffected part of the rope is pulled sideways when the part next to it moves sideways
What is polarisation?
Transverse waves are plane-polarised if the vibrations stay in one plane only
Longitudinal waves cannot be polarised
What is meant by unpolarised waves?
This is if the vibrations change from one plane to another
Light from a filament lamp or a candle is unpolarised. If unpolarised light is passed through a polaroid filter what happens?
The light transmitted is polarised as the filter only allows through the light which vibrates in a certain direction, according to the alignment of its molecules
What happens if unpolarised light is passed through two Polaroid filters, what would happen with the transmitted light?
If unpolarised light is passed through two Polaroid filters the transmitter light intensity changes if one Polaroid is turned relative to the other one
The filters are said to be crossed when the transmitted intensity is minimum