10. Diffraction Gratings Flashcards
How can you carry out the Double-Slit experiment using a single source?
Using a diffraction grating with hundreds of slits per millimetre a Single laser source can make an interference pattern with greater accuracy than the double-slit experiment due to the greater number of beams reinforcing each other.
How does a diffraction grating allow a single wave source to complete the Double-Slit Experiment?
As there are many more slits within the diffraction grating, when a light wave passes through them, many more waves are diffracted through the grating, causing more waves to interfere with each other, this causes the bright fringes to become thinner but brighter, and the dark fringes to become darker and thicker.
How can you tell the different fringes apart?
The one which is straight ahead of the source is the zero order line, the 2 lines above and below it are the 1st order, the ones above and below them are the second on, and so on.
What is the diffraction grating equation?
The diffraction grating equation can be written as the distance between the slits multiplied by the sin of the angle between the 0th and 1st order lines is equal to the number of orders multiplies by the wavelength of the light source in metres.
d*sinθ = nλ
What conclusions can you draw from this equation?
If λ is bigger, sinθ will also be larger, so as the wavelength of the light grows, the distance between fringes also grows.
If d is bigger, sinθ is smaller, this means that the coarse the grating, the less that pattern will be spread out.
Values of sinθ greater than 1 are impossible, so if a order of magnitude gives a result greater than 1 for θ, this order does not exist.
