10. Diffraction Gratings

Question 1

What is a diffraction grating?

Answer 1

Contains lots of equally spaced slits very close together and allows for sharper interference patterns

Question 2

What is the equation for diffraction grating?

Answer 2

d sin θ = n λ

d = distance between slits (m)
θ = angle to the normal made by maximum (degrees or radians)
n = order of maximum

Question 3

What are the conclusions from the diffraction grating equation?

Answer 3

1. If λ is bigger, sin θ is bigger and so θ is bigger. This means that the larger the wavelength, the more the pattern will spread out
2. If d is bigger, sin θ is smaller. This means that the coarser the grating, the less the pattern will spread out
3. Values of sin θ greater than 1 are impossible so if for a certain n the result is more than 1, that order does not exist

Question 4

What do astronomers and chemists use the diffraction grating for?

Answer 4

To analyse the spectra of stars and the spectra of certain materials to see what elements are present because diffraction gratings are more accurate than prisms

Question 5

How are diffraction gratings used in X-ray crystallography?

Answer 5

The crystal acts as a diffraction grating and the spacing between atoms (slit width) can be found from the diffraction pattern

Question 6

What did X-ray crystallography lead to?

Answer 6

The major discovery of the structure of DNA