Sample Exam
Sample Exam
Sample Exam
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Diffraction [20 Points]<br />
The emission of light from an excited gas is focused and passed through a<br />
diffraction grating with 3000 lines/cm, as shown. First order and second<br />
order spectral lines are observed.<br />
a) Four first-order spectral lines are observed at 7.07°, 7.48°, 8.38°, and<br />
11.3°. Find the wavelengths of these four spectral lines. [8 Points]<br />
Answer: λ 1 = 410 nm, λ 2 = 434 nm, λ 3 = 486 nm, and λ 4 = 656 nm<br />
b) At what angles are the second-order spectral lines observed? [7 Points]<br />
Answer: θ 1 = 14.2°, θ 2 = 15.1°, θ 3 = 17.0°, and θ 4 = 23.2°<br />
c) Suppose the diffraction grating is replaced with another having twice the<br />
number of gratings/cm. Find the angular separation observed between<br />
the second-order spectral lines. [5 Points]<br />
Answer: Δθ = 22.5°