Diffraction And Interference Flashcards
Experiment that demonstrates the photons in coherent light
Youngs double slit experiment
What is coherent light
Light composed of one consistent phase different and same frequency
What causes the areas of light and dark in young double slit experiment
Interference of the light as they meet at certain points
Why do fringe patterns occur
Coherent light passes through one of two of the slits and then due to diffraction causes interference
How does diffraction through 2 slits cause interference
Diffraction causes light to change in phase difference so some light combines and cancels and others combine
How out of phase is light when there is a dark fringe
180 or pi out of phase
How out of phase is light when in the light fringes
Same phase as each other
How small is a nanometer in meters
10^-9
What’s the equation for fringe separation
W= λD / s
What is W in fringe separation equation
Fringe separation
What is D in fringe separation equation
The distance from slits to screen
What is s in fringe separation equation
The slit spacing
Fringe separation increases when
Distance from screen increases
λ increases
The slit spacing is decreased
Why are double slits called coherent
They emit light waves of the same frequency with a constant phase difference
Does wavelength of light affect fringe separation
Yes the separation is greater for red light than it is for blue light
A laser is useful as
It’s a convenient source of coherent light
How do white light fringes differ to laser fringes
The fringes show the full spectrum of colours in white light
Inner fringes tinted blue
Outer fringes tinted red
What is diffraction
The spreading of waves as they pass through a gap
What 2 factors cause waves spread out more as they pass through a slit
Gap is made narrower
The wavelength is made larger
What pattern does diffraction of light take up when passing a single slit
A central maxima then matching smaller peaks until they are then negligible
What’s unique about the widths of the outer fringes of a single slit
Each of the outer fringes are the same width
What unique about the width of the central fringe in a single slit diffraction
The central fringe is twice as wide as the outer fringes
What unique about the intensity of the outer fringes in single slit diffraction
The outer fringes are much less intense than the central fringe
What is a diffraction grating
A plate with many closely spaced parallel slits on it
What pattern does a diffraction grating take when monochromatic light take
A central order with multiple orders around it numbered from the centre
What increases the angle of diffraction between each transmitted beam and the central beam
Light of a longer wavelength
A grating with closer slits
Equation of diffraction grating
d Sin θ = n λ
What does d mean in diffraction grating equation
Grating spacing
What does n mean in diffraction grating equation
Number order of the beam (how many beams it is away from the central order
3 types of spectra
Continuous spectra
Line emission spectra
Line absorption spectra
What light source emits a continuous spectrum
A filament light
What light emits a line emission spectra
A vapour lamp or a discharge tube
What combination of factors creates a line absorption spectra
A filament light as it passes through a glowing gas
