PHYS 142 Lecture Notes - Lecture 34: Diffraction Grating, Diffraction, Spectroscopy

• School: McGill University
• Department: Physics
• Course: PHYS 142
• Professor: Guillaume Gervais

Document Summary

Phys 142: electromagnetism and optics - lecture 34 : wave optics part 2. The diffraction grating is a device containing many slits, each of which becomes the source of a light wave that undergoes diffraction. Each light ray from a slit travels a distance r = d. sin farther than the one from the slit adjacent to it. Light waves from different slits will all be in phase with each other when they arrive at a point on the screen with an angle m such that dsin m=m where m=0,1,2,3 . Positions of the bright fringes: ym=l tan m. The name of the m integer (in m is called the order of diffraction. As n increases, the fringes get brighter and narrower (due to conservation of energy. Bright fringes from a diffraction grating are much sharper and much more distinct than those where i is the intensity from a single slit. I max=n 2 i from a double slit interference pattern.