Interference Flashcards
when is a pattern of maxima and minima produced if waves from different sources overlap
- if the waves combine constructively or destructively
- at fixed positions relative to the sources
what is this effect called
interference
what is the path difference of two waves
- the number of wavelengths they are ‘away’ from each other
- measured in radians
what is a misconception about path differences
- that they are the number of wavelengths out of phase with each other
- two waves could have a path difference of 6 pi meaning there is q distance of three wavelengths between them
- however they are in phase because they are perfectly 3 wavelengths apart
when do positions of maximum amplitude occur when waves interact and why
- when the path difference is 0
- or a whole number of wavelengths
- because the waves are always in phase so constructive superposition occurs
when would the amplitude of a wave be zero when waves interact and why
- when the path difference is an odd half wavelength
- because the waves would be pi radians out of phase
- meaning destructive superposition takes place
what three conditions need to be met in order for a stable interference pattern to occur
- the waves are of the same type
- the sources are coherent
- the wave have similar amplitude at the point of superposition
what does it mean for sources to be coherent
- they have the same frequency
- and maintain a constant phase relationship
if you have two sources of ripples close to each other which creates ripples with crests and troughs, when would constructive interference take place
when a crests of one ripple interfere with the crests of the other
when would destuctive interference occur
when the crests of one ripple interfere with the troughs of the other
in the double slit experiment where you have two waves entering two slits and interfering with each other, what would be points n or Px (P0 for example) be noting
the maxima of the new wave that has been formed from the interference between the two waves
where would those points therefore be if maxima were being formed
they would be point where the waves were constructively interfering
when the two waves constructively interfere, several maxima are formed next to each other, starting from the centre one (P0) to the left and right ones. if P0 is the central maximum, what is the path difference between the two waves at this point and why
- it is 0
- because if it is the central maximum it means both waves have had to travel equally far distances to reach that point
- and as the waves have to have the same frequency, it means that there is no difference in the number of wavelengths it took to reach the point P0
- essentially the waves are always in phase in this case
what would path difference for the first maximum and second maximum (P1 AND P2) on either side of the central maximum be and why
- P1 would have a path difference of pi
- P2 would have a path difference of 2 pi
- this is because at P1 and P2 the waves are still in phase
what would be done in order to calculate the wavelengths of a type of wave using the double slit experiment
- place a sheet of paper on a vertical surface
- mark the position of the aerial at the highest available maximum
- pencil the position of the slits onto the paper and measure the distance between each slit from the maximum
- use a formula to calculate the path difference