Physics

what are the differences between two slit interference and a diffraction grating

• brighter

• more defined

• further spread/larger range

why does a diffraction grating cause brighter maximas

more slits means more light gets through hence the brighter maxima

why does a diffraction grating cause a more defined separation between maxima and minima - narrowed maxima, widened minima

if the adjacent slits are even slightly out of phase the overall resulting interference from many of the slits is destructive

why is the spread of a diffraction grating larger

the slit spacing, d, is much smaller and because of nλ=dsinθ when d decreases, θ must increase

because the angle between the centre maxima and next maxima is greater this shows a greater area covered by the pattern → from triangle

do long or short wavelengths diffract more around a barrier

long

how does wavelength impact spacing of an interference pattern

higher wavelength means greater spacing

how does distance of wave sources from screen impact spacing

increased distance increases spacing

how does the separation of the sources impact spacing

increase in separation decreases spacing

does the refractive angle increase or decrease when going to a medium with lower refractive index

increas

does the refractive angle increase or decrease when going to a medium with higher refractive index

decrease

what does n stand for

refractive index

what is needed for total internal reflection

θ_i must be greater than θ_c

• the critical angle is θ_i when θ_r is 90°

needs to be going from a higher refractive index to a lower refractive index

what is needed for something to arrive out of phase

path difference needs to be an odd number of half wavelengths (n-1/2)λ

what is needed for waves to arrive in phase

path difference needs to be a whole number of waves (nλ)