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6. While looking through a diffraction grating at a Nitrogen discharge tube you

ID: 2256385 • Letter: 6

Question

6. While looking through a diffraction grating at a Nitrogen discharge tube you note that light with a known wavelength of 5679D is visible at an angle of 37 from the central antinode. How many slits are there in this diffraction grating for each millimeter of width?

7. You are looking through a diffraction grating, which contains 520 slits for each millimeter of width, at a light source emitting light with a wavelength of 5890D. At what angles will the first and second order antinodes be visible?

Explanation / Answer

d sin theta = mL

d = 1 * 5679*10^-10/(sin 37)

d = 0.000946 mm

no. of slits per mm = 1056 slits per mm


b. for first order

d = 1/520 = 1.9 um

so sin theta = 1* 5890*10^-10/1.9um

sin theta = 0.3100

theta = 18.05 deg

for second order

tsin theta = 2* 5890 *10^-10/1.9 um

theta =sin -1( 0.62) = 38.31 deg