A student wishes to determine an unknown wavelength of light using a diffraction grating
PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics
Problem
A student wishes to determine an unknown wavelength of light using a diffraction grating. The experiment proceeds as follows:
• A helium spectral line of known wavelength 588nm is directed normally onto the grating, and its second-order bright maximum is measured at an angle of 22.0∘ from the central axis.
• Without moving the grating, the student then shines the unknown light on the grating and finds that its first-order bright maximum occurs at 17.5∘.
Assume measurements are made in air and that the small refractive index difference from vacuum can be neglected.
Use the data above to respond to the following tasks. Show all mathematical steps and include units with final answers.
(a) Determine the spacing between adjacent slits on the diffraction grating.
(b) Using your answer from part (a), calculate the wavelength of the unknown light.
(c) For the wavelength found in part (b), determine the highest order bright maximum that the grating could, in principle, produce. State whether the third-order maximum for this wavelength would be observable and justify your answer.