5.7 The diffraction grating

Question 1

Define diffraction grating

Answer 1

a plate with many closely ruled parallel slits on it

Question 2

Why is light transmitted by the grating in certain directions only?

Answer 2

• light passing through each slit is diffracted
• the diffracted light waves from adjacent slits reinforce each other in certain directions only, including the incident light direction and cancel out in all other directions

Question 3

What causes the angle of diffraction between each transmitted beam and central beam to increase?

Answer 3

• light of a longer wavelength is used

- grating with closer slits is used

Question 4

What equation is used for diffraction grating?

Answer 4

dsinθ=nλ

Question 5

What creates a bigger angle of diffraction?

Answer 5

For a given order and wavelength, the smaller the value of d, the greater the angle of diffraction.

The larger the number of slits per metre, the bigger the angle of diffraction.

Question 6

How do you calculate the number of maxima observed?

Answer 6

2n+1, where n is the greatest order