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
