Chapter 11: Waves Flashcards
cause of wave
something making particles or fields oscillate at a source
progressive wave
carries energy from one place to another, no transfer of material
what happens to a wave as it moves further from a source
source loses energy
displacement
how far a wave travelled from a position of equilibrium
amplitude
maximum magnitude of displacement
wavelength
length of one whole wave oscillation
period
time taken for a single whole oscillation
frequency
number of waves that pass a point per second
phase
measurement of a position of a certain point along a wave cycle
phase difference
amount by which one wave lags behind another, difference in phase between two points on a wave
transverse
oscillations are perpendicular to the direction of energy transfer
longitudinal
oscillations are parallel to the direction of energy transfer
how is phase difference measured?
angles or in radians, fraction of a cycle
What are two ways you can model transverse waves?
- displacement/distance graph
-displacement/time graph
reflection
changes direction at the boundary of two medium, remains in original medium
what is the law of reflection
angle of incidence = angle of reflection
what stays the same during reflection?
wavelength and frequency
wavefront
line joining points of the wave which are in phase
what is the distance between wavefronts called?
wavelength
refraction
changes direction as speed changes, one medium to another
partial reflection
always some reflection when the wave refracts
What does it mean when a wave bends towards the normal?
wave slows down
What does it mean when a wave bends away from the normal?
wave speeds up
do sound waves behave the same when travelling through mediums as electromagnetic waves?
no.
they speed up in denser mediums
what happens to the wavelength if the wave slows down
decreases
what do each of the ‘axes’ on an oscilloscope measure?
vertical divisions: voltage/amplitude
horizontal divisions: time
True or false: Diffraction is most noticeable when the wavelength is much larger than the gap the wave is travelling through
False.
Most diffraction is seen when the gap and the wavelength are the same size
What type of waves can be polarised?
only transverse waves
what is a polarised and unpolarised wave?
Polarised waves only contain waves oscillating on one axis
Unpolarised waves can be oscillating in any direction perpendicular to the axis of propagation
Ripple tank diffraction experiment
1) Create water waves
2)Vary the size of the gap they pass through
3) Note how the direction of the wave changes
Intensity equation
power / area
What happens to the intensity of light during rotating polarisation filter?
varying from a maximum to minimum when axes are perpendicular
how are intensity and amplitude related?
intensity is directly proportional to amplitude^2
What is the range of wavelengths for visible light?
400-700 nm
How do you polarise microwaves?
using a metal grid as they have larger wavelengths
refractive index
measure of how fast light travels in a material compared to the speed in a vacuum
What is the formula for refractive index?
n = c/v
n - refractive index
c - speed of light in vac
v - speed of light in material
critical angle
angle of incidence at which light will reflect off a boundary rather than refracting in the medium
critical angle formula
sinC = 1/n
total internal reflection
the phenomenon that happens to light when incidented beyond the critical angle
