4.1 Waves and vibrations Flashcards
what are waves that pass through a substance the same as
vibrations that pass through that substance
how are sound waves that pass through the air created.
by making a surface vibrate so it sends compression waves through the surrounding air
examples of waves that pass through a substance (mechanical waves)
sound waves
seismic waves
waves on string
what happens when waves pass through a substance
the particles in the substance vibrate in a certain way which makes nearby particles vibrate in the same way and so on
description of electromagnetic waves
oscillating electric and magnetic fields that progress through space without the need for a substance
how em waves work
the vibrating electric field generates a vibrating magnetic field which vibrates a further electric field and so on
which way is the direction of vibration of the particles of a longitudinal wave
parallel to the direction in which the wave travels
examples of longitudinal waves
sound waves
seismic waves
P waves
slinky
what is it called in a longitudinal wave when the waves are close together
compression
what is it called in a longitudinal wave when the waves are far apart
rarefaction
which way is the direction of wave vibrations in a transverse wave
perpendicular to the direction in which the wave travels
examples of transverse waves
electromagnetic waves
S waves
waves on a wire/ string
waves on water
when are transverse waves plane polarised
if the vibrations stay in one plane only
if the vibrations change from one plane to another the waves are unpolarised
what cannot be done to longitudinal waves
they can’t be polarised
how does unpolarised light from a lamp or a candle become polarised
if passed through a polaroid filter
the transmitted light is polarised as the filter only allows light through which vibrates in a certain direction according to the alignment of the filters molecules
if unpolarised light is passed through 2 polaroid filters what is the transmitted light intensity charge according to
if one polaroid is turned relative to the other one
when are the polaroid filters said to be crossed
when the light intensity emitted is a minimum
because the polarised light from the first filter can’t pass through the second filter as the alignment of of molecules in the second filter is 90 degrees to the alignment in the first filter
what is the plane of polarisation of an electromagnetic wave defined as
the plane in which the electric field oscillates
what do polaroid sunglasses do
reduce the glare of the light reflected by water or glass
the reflected light is polarised and the intensity is reduced when it passes through the sunglasses
