5 marksLight from a laser pointer was passed through a diffraction grating. The light was perpendicular to the diffraction grating as shown. A diffraction pattern was produced on a screen.
The distance between the first order maximum and the central maximum of the diffraction pattern was 
. The distance between the diffraction grating and the screen was D.
Distance was measured to be 0.500 m with a metre rule. The wavelength of light 
from the laser pointer was 650 nm.
The laser pointer was replaced with one that produced light of a different wavelength. The new distance was measured to be 0.400 m.
D = 1.45 m
Calculate the wavelength 
of the light emitted by the replacement laser pointer.
= .......................................................
2 marksExplain one modification to this method that would decrease the uncertainty in the calculated value of .
3 marksIn another experiment, the light from the laser pointer was not quite perpendicular to the screen.
Explain how this would change the diffraction pattern produced on the screen.
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