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09 interference and lasers online

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Physics 110
Diffraction Gratings/Laser
Lab # ____ Name ____________________________________________________ Date _________
Lab Partner(S) ____________________________________________________________________
Online lab
The purpose of this exercise is to study the properties of diffraction gratings. A diffraction grating
consists of a large number of equally spaced slits or rulings on a flat surface. The purpose of a
grating is to break light up into its spectrum of colors. The basic grating equation is
  = d(x/L)
is the wavelength of the light, d is the slit separation distance, m is an integer and is the
order of the spectrum, and θ is the angle to which the wavelength λ is diffracted by the grating.
When the angle is small (<10
) the equation can be approximated by d(x/L), where d is the same,
and x is the distance of the bright spot from the center line, and L is the distance from the diffraction
grating to the screen.
The online lab simulates a monochromatic light source passing through a diffraction grating and
shining on a screen. You can adjust various parameters of the experiment and view the
interference pattern that occurs.
A. Open the link above and observe the set up.
B. Set the lens to grating distance to 5.0 m
C. Set the grating lines per mm to 200
D. Set the wavelength to 532 nm
E. Record the distance to the first two bright spots on either side of the central spot.
Repeat steps A -E for a wavelength of 650 nm
Repeat steps A E for grating lines per mm of 400 (532 wavelength)
A. Calculate the position of the maximums using the diffraction equation.
B. Calculate the percentage error between your calculated value and the measured value
V. Questions
A. What general relations can be made about the diffraction grating and the patterns produced
B. Do you think there is anything that you could do that would decrease your percentage error?

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