| what four properties do all waves undergo | reflection
refraction
diffraction
interference |
| what is meant by coherent waves | waves with a constant phase difference |
| how do you produce coherent waves | by using a single source |
| what is meant by waves that are "in phase"/constructive interference | when crests meet crests and troughs meet troughs for waves with the same: frequency velocity wavelength |
| what is meant by waves being out of phase/destructive interference | two waves which have the same frequency, wavelength and velocity, if a crest coincides with a trough and a trough coincides with a crest |
| what is the test for a wave | destructive interference |
| when is an interference pattern produced in water waves | when two sets of circular water waves overlap and combine |
| if two loud speakers are connected to the same source, is the sound produced coherent? | yes, because it has the same frequency, the same wavelength and is produced with a constant phase difference |
| what does the interference pattern of sound waves look like? | patterns of loud and quiet |
| when does a maximum occur in an interference pattern? | when the path difference is is a whole number of wavelengths
(Path difference = mλ (where m = 0,1,2,3...)) |
| when does a minimum occur in an interference pattern | when the path difference is a whole number of wavelengths PLUS half of a wavelength
(Path difference = (m + ½)λ (where m = 0,1,2,3...)) |
| what is meant by path difference | path refers to the distance a wave has travelled to get to a point
path difference refers to the distance between the path of two points |
| what is the path difference of two waves travelling to the central maximum | 0 |
| how is an interference pattern produced using light | the light source is passed through a blackened slide which has two parallel slits to allow light through |
| why is a laser used as a light source when producing an interference pattern | it is a monochromatic light source (single frequency) |
| what does the screen show when a laser is passed through the double slit | the screen shows a bright central point, with a pattern of light and dark patches on either side, showing constructive and destructive interference |
| what is meant by slit separation (d) | the distance between slits on a grating |
| what is the formula for the relationship between number of maxima, wavelengths, slit separation and angle between screen and light source | mλ=dsinθ
where m is the number of maxima (or minima)
λ is the wavelength
d is the slit separation
sin θ is the sine of the angle between the screen and the light source |
| in the formula mλ=dsinθ, what is meant by m? | order number
NOT total number of maxima
if you are looking at the third order maximum, m=3 |
| how do you make the pattern of light and dark areas (fringes) brighter and sharper | more light is needed
this is done by using a grating which has multiple splits |
| how is slit separation calculated | calculating the number of lines in every mm |
| what happen to angle if we increase the number of lines per mm on a grating | d decreases
the angle between the central fringe and the fringe being measured will increase |
| what happens to angle between central fringe and the fringe being measured if we increase the wavelength of light being put through a grating | it will increase |
| what happens to distance between maxima when you decrease the distance between slits on a grating | it will increase |
| what happens to distance between observed maxima if you increase the distance between the laser and the grating | it will decrease |
| what happens to distance between observed maxima if you increase the distance between the grating and the screen | it will increase |
| what colour is refracted most when white light passes through a prism | blue light |
| what happens when white light passes through a prism | one bright spectrum is produced (by refraction)
red refracts the least |
| what happens when light passes through a diffraction grating | multiple less bright spectra are produced (by interference)
red refracts the most
the central image is white |
| what happens to spectra further out when light passes through a diffraction grating | spectra further out may overlap, making it difficult to decide what colours are seen |
| which colours of light would give the smallest angle between the central maximum and the first order maximum | light with the shortest wavelength
this is because the wavelength is smallest
the smallest wavelength gives the smallest sin of the angle, therefore the angle is the smallest |
