Interference Flashcards
Phase difference equation
Phi=2pix/λ
Phi is phase difference in radians
x is x displacement of wave in m
λ is wavelength
Constructive interference equation
l1-l2=m* λ
l is length
m is an integer
λ is wavelengths of the coherent waves.
Destructive interference occurs when
l1-l2=(m+1/2) λ
Optical path difference equation
OPD=n*gpd
gpd is distance travelled in medium in metres.
Process for OPD with on wave in medium and one not in medium
OPD= (n1-n2)*gpd.
Where n1>n2
Reflection low to high n has a phase change of ….. radians
Pi
Reflection from high to low has a phase change of… radians
0
Pi radians reflection
If wave went crest first reflected will be trough first.
Interference by division of amplitude is when
A wave is split and then recombined to have a greater amplitude or no amplitude
Deriving equation for thin film division by amplitude
OPD=m λ or (m+1/2) λ
Since being reflected it will travel d twice so
2dn=m λ..
if high to low reflection
2dn + λ/2= m λ…
Equation for minimum thickness to give destructive interference
d= λ/4n
Wedge fringe separation equation
Deltax= λ*l/2d
Where delta x is fringe separation in m
λ is wavelength
l is length of wedge
d is height of the gap of wedge
Interference by division of wavefront
When two wave separated by diffraction combine to interfere constructively or destructively
Young slit experiment equation
Delta x = λD/d
Delta x is the fringe separation
λ is wavelength
D is distance from slits to wall
d is distance between two adjacent slits
Can longitudinal waves be polarised?
No, only tranversw
Can transverse waves be polarised?
Yes
What happens when light is directed through a slit but it hits it an angle
Component parallel will be transmitted but component perpendicular will be blocked.
How to work out angle of polarisation?
Use Brewsters Law equation
Brewsters law equation
n=tanip
