P4 Flashcards
what do waves transfer and what don’t they transfer?
they transfer energy and information but not matter.
what is the frequency of waves?
the number of waves per second (HZ)
what is the wavelength of a wave?
the distance between two peaks ( M)
what is the amplitude of a wave?
the distance from the centre line to the top of a peak or the bottom of a trough.
what is the period of a wave?
how long it takes a particle in a wave to do one whole vibration. time period=
1/ frequency.
what is the velocity of a wave?
the frequency x the wavelength.
what is the difference between transverse and longitudinal waves?
transverse is where the energy is transferred perpendicular to vibrations whereas longitudinal is where energy is transferred parallel to vibrations.
give examples of transverse and longitudinal waves.
water waves and seismic waves are transverse and electromagnetic radiation.
sound waves and waves in a stretched spring are longitudinal.
what is the wave speed equation?
wave speed=
frequency X wavelength.
what is the other wave speed equation involving distance and time?
wave speed= distance/ time.
how do you measure the velocity of sound in air?
the clap echo method or a computer timed method.
time it takes a sound to travel a measured distance must be recorded. the distance must be large over 50 metres or the time recorded on an electronic timer (to eliminate errors due to reaction time).
how do you measure the velocity of waves on water?
you measure the distance between two points. the time how long it takes the wave to travel between those two points.
what is refraction?
when Sound waves or light waves change speed as they pass across the boundary between two substances with different densities, such as air and glass. This causes them to change direction.
how does the direction of a wave change when it goes from one material into another?
the light slows down going into a denser substance, and the ray bends towards the normal
the light speeds up going into a less dense substance, and the ray bends away from the normal.
what are some of the effects of the refraction of light?
A clear pool of water always appears to be shallower than it actually is.
A coin placed at the bottom of beaker containing water seems to be raised.
A stick partially dipped in water seems to be bent.
The sun appears flattened at the time of sun set and sun rise.
why can a change in wave speed cause a change in direction?
if the wave is entering the medium at an angle, then part of the wave enters the medium first, and starts to slow down, while the other part of the wave is still going fast, and therefore the wave must bend. If the wave enters at a right angle, then the entire wave is slowed down simultaneously and no refraction occurs.
what are some of the effects of waves being reflected?
smooth surfaces reflect waves whereas rough surfaces scatter them around in all directions?
what is absorbtion and transmittion?
The light wave could be absorbed by the object, in which case its energy is converted to heat. The light wave could be reflected by the object. And the light wave could be transmitted by the object.
