Double slit experiment and Diffraction gratings Flashcards
What is young’s double slit formula?
What does each letter stand for?
W = λD/S
W - fringe spacing
D - distance between slits and the screen
S - Distance between slits
Why is a diffraction grating used?
Produces brighter and narrower bands and darker areas, sharper interference pattern, allows for more accurate measurements
What’s the line of maximum brightness at the centre called?
Zero order line
What’s the diffraction grating equation?
What does each letter stand for?
d sinθ = nλ
d - distance between slits
θ - the angle to the normal made by the maximum
n - order of maximum
λ - wavelength of light source
If the grating has N slits per metre, what is the slit spacing?
1/N
What conclusion can you draw from the diffraction grating experiment about the wavelength?
- If λ is bigger, sinθ is bigger therefore θ is bigger. So the bigger the wavelength the more the pattern will spread out
What conclusion can you draw from the diffraction grating experiment about the distance between slits?
- If d is bigger, sinθ is smaller, so the coarser the grating the less the pattern will be spread out
What conclusion can you draw from the diffraction grating experiment about the value sinθ?
Sinθ values greater than 1 are impossible, because then the angle would have to be greater than 90 which is not possible
What are the uses for diffraction gratings?
Line absorption spectra from stars - different elements in the star’s atmosphere absorb light of different wavelengths
What is x-ray crystallography?
The average wavelength of x rays is of a similar scale to the spacing between atoms in crystalline solids, this means if x rays are directed at a thin crystal a diffraction pattern will form. The spacing between the atoms can be found from the diffraction pattern. The structure of DNA was found with x ray crystallography
