Question

1. Short wavelengths of light passed through a diffraction grating create fringes that are _____ than long wavelengths of light.

more spread out

more compact brighter

None of the above

12. The spacing of the diffraction pattern on a viewing screen does not depend on the distance from the diffraction grating to the screen.

True

False

2. A transmission diffraction grating produces a diffraction pattern with the first order angle at 35 degrees when light with a wavelength of 600 nm is used, meaning the grating has _____ lines/mm.

0.001

956

1046

None of the above

3. The path length difference between the zeroth order bright fringe and the first order bright fringe of a diffraction grating is _____.

zero

one-half wavelength

one wavelength

None of the above

4. A diffraction grating with 1000 lines per millimeter has a first order diffraction angle of 25 degrees, so the wavelength of light being used is _____ nm.

423

0.0004

250

None of the above

Answer 1

• Short wavelengths of light passed through a diffraction grating create fringes that are more compact than long wavelengths of light.

it is so because , according to the diffraction equation , is directly proportional to the Sin() , thus more is the wavelength () , more is the and ultimately shorter wavelength have compact fringes as compared with the longer wavelengths.

• The spacing of the diffraction pattern on a viewing screen does not depend on the distance from the diffraction grating to the screen. - FALSE ,

it is so because , according to the diffraction equation :

where depends on the distance between the diffraction grating and the screen.

• A transmission diffraction grating produces a diffraction pattern with the first order angle at 35 degrees when light with a wavelength of 600 nm is used, meaning the grating has 956 lines/mm

according to the diffraction equation :

1*600 * 10^(-9) = d Sin(35)

d = 1.046 * 10 ^{-6} m

therefore no. of lines per mm = 1/1.046 * 10 ^{-6} m * 1000

= 956

• The path length difference between the zeroth order bright fringe and the first order bright fringe of a diffraction grating is one wavelength .

It is so because the fringe width is directly proportional to the wavelength of the light used.

• A diffraction grating with 1000 lines per millimeter has a first order diffraction angle of 25 degrees, so the wavelength of light being used is 423 nm                                                    

using diffraction equation

1*wavelength = (1/1000*1000) Sin(25)

wavelength = 423 nm

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