Physics 012 1st Edition Lecture 28 Outline of Last Lecture I. Double-slit experimenta. When L is much larger than d, you can assume the two light beams (from each slit) are essentially parallel.i. d = distance between slits, L = distance between screens, m = fringe order(central = 0, first = 1, etc.), λ = light wavelength, θ = angle the normal line to the first screen and the light beams, y = vertical displacement of the light beamsii. dsinθ = mλ (for constructive interference)iii. tanθ = y/Liv. y = (mλL)/dII. Diffraction GratingsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Like double-slit experiment but with many slits.b. d = distance between 2 successive slitsc. If experiment were in a medium other than air: y = [(mL)/d][λvac/n]III. Change in Phase Due to Reflectiona. When a light beam is going from a medium with a lower index of refraction to a medium with a higher index of refraction (n1 < n2), the reflected light will undergoa phase change.i. The reflected light will be out of phase by exactly half a wavelength (λ/2).ii. No phase change occurs when n1 > n2.IV. Thin Film Interferencea. t = thickness of film, ray 1 = ray reflected from top of film, ray 2 = ray reflected from bottom of filmb. Assume angles of refraction through the film are very small, so the extra distancetraveled by light through the film is about 2t.c. Ray 1 has undergone a phase change. Ray 2 has not undergone a phase change. Ray 1 and 2 will be out of phase.d. Ray 2 has a different wavelength while traveling through the film.i. λ` = λvac/nfilmOutline of Current Lecture
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