M4.2 Waves Flashcards
define period
the time taken for one wave cycle
phase difference
difference between two points on waves.
i.e difference between two corresponding peaks
what do all electromagnetic waves transfer
energy
why does a wave move back down after up
after being moved from the equilibrium a restoring force is applied to the wave which pulls it down
what is 180 degrees in radians
pi radians
what is the law of reflection
angle of incidence = angle of reflection
which direction does the wave defract when it enters a more dense material
towards the normal because it slows down
why does white light into a prism make a rainbow
because low frequency waves slow down
what is diffraction
waves spreading out when they passthrough a gap or around an object
what determines the degree of diffraction
relative size of the slit
or around an obstical the wavelength
describe the structure of an unpolarised electromagnetic wave
split into two waves magnetic and electric perpendicular to each other
define unpolarised electromagnetic waves
EM waves in all vertices
define polarisation
polarisation is when an unpolarised wave travels through a polarisation filter which makes it oscilate in one direction
explain intensity
intensity and distance have an inverse square law
intensity is the power per cross sectional area
i.e energy doesnt change but the wave spreads out more
what is snells law
n sin(theta) is constant
define the refractive index
ratio between speed of light in a vacuum and speed of light in the material
What is the critical angle
the angle of incidence that creates an angle of refraction of 90 degrees
define total internal reflection
when the angle of incidence is larger than the critical angle the light is instead reflected at the boundary rather than passing through
(looks like the light bounces back into the glass rather than leaving)
describe PAG to measure critical angle
get a semi circlular glass block shine a ray into the glass block
Aimed at the middle of the flat edge
meassure the angle of incidence to before the ray leaves the block
use n sin(theta) is constant to find the refractive index
then use n sin(theta) to find theta when the angle of refraction is 90
what is path difference at a maxmia
nλ
define stationary wave
two super imposed waves in a string same frequency
what is a node
points with 0 displacement
why do nodes occur
because if they have equal frequencies then both will have 0 displacement at the same point 0 + 0 is 0
what is an anti node
point with maximum displacement
when not in a pipe what is the minimum wave length of a stationary wave
1/2 λ* n
what is there at an open end of a pipe
anti node
what is there at a closed end of a pipe
nodes
what is the smallest wave length when the pipe is closed at one end and what length does each harmonic increase by
1/4 λ
2/4 λ (alway has an odd number on top)
what is the minimum length when the pipe open at both ends
1/2 λ
What is the relationship between intensity and amplitude
Intensity is directly proportional to A^2
what is the range of wavelengths for a radio wave
Radio 10^6 -> 10^-1m
what is the range of wavelengths for a mirco wave
Micro 10^-1 -> 10^-3
what is the range of wavelengths for a infrared wave
10^-3 -> 10^-7
wavelength range for visble light
700 nm to 400 nm
what is the range of wavelengths for a ultraviolet
400nm -> 10*10-8
what is the range of wavelengths for an x ray
10^-8 -> 10^-10
what is the range of wavelengths for gamma rays
10^-10 and lower
