Diffraction gratings

Question 1

What Equipment should be used in this experiment?

Answer 1

• Laser
  -Diffraction grating
  -White screen
• Metre ruler

Question 2

What method should be used?

Answer 2

• Ensuring that the laboratory is partially darkened, set up the apparatus as shown in the diagram.
• Adjust the apparatus so that D is 1m, measured using the metre ruler

-Measure the distances and on either side of the central maximum using the h1 h2 ruler and find the mean of each of them.

Question 3

What graph and calculations should be used?

Answer 3

• Work out the slit separation by finding the reciprocal of the number of slits per metre quoted on the diffraction grating.

-Find and by using θ1 θ2 by using θn = arctan( hn/D)

-Find λ from both of these angles using λ=dsin(θ)/n and then calculate the mean.

Question 4

What Safety precautions could be taken?

Answer 4

-Use proper signage

-point lasers down not into someone eye

Question 5

What Improvements could be done?

Answer 5

Make sure that the screen and double slit are aligned perfectly normal to the laser to avoid parallax error in the measurement of the fringe width. A set square can be used in conjunction with the ruler.