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Diffraction of White Light Using a Diffraction Grating

المؤلف:  Will Raven

المصدر:  Atomic Physics for Everyone

الجزء والصفحة:  p-28

2026-11-12

31

Let’s put the screen 10 cm from the grating. On the screen is a ruler that will serve as our z-axis. If the grating wasn’t in place, all spectral components would hit the screen at the same place. Let’s call this spot z = 0 cm. With the grating in place and the white light hitting the grating perpendicular, the blue light, which diffracts at 26.7◦, hits the screen at z = (10 cm)tan 26.7◦ = 5.04 cm while the green light hits the screen z = 6.28 cm. You could also skip the angle calculation and use the formula:

for incident light perpendicular to a transmission grating,

where L is the distance between the diffraction grating and the screen. z is positive for positive m and negative for negative m. You have the opportunity to derive this formula in problem 2.4. Notice that the diffraction order in the denominator is squared, so the sign of m only determines the sign of z.¹ 

_{1. A diffraction grating spatially separates the components of white light according to their wavelengths, producing distinct colors at different positions on the screen. The diffraction order determines the direction of the light, while its wavelength determines its position.}