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Unformatted text preview: Experiment 7 Young’s Double Slit Experiment And Its Variation Introduction This week’s lab explores the wave nature of light as established by the Young’s Double Slit experiment and a variation on this theme known as Lloyd’s Mirror Experiment. The principle of these is illustrated in Fig. 13C, Jenkins and White, reproduced below. A C B S 1 S 2 S Figure 1: Experimental arrangement for Young’s double-slit experiment P ∑ S P y X S 1 S 2 d θ θ ` Figure 2: Path difference for Young’s double-slit experiment A narrow source slit, S , is illuminated with monochromatic light of wavelength λ . Cylindrical waves thus generated, in turn, illuminate two narrow slits S 1 and S 2 , located symmetrically about S , with the separation between S 1 and S 2 being d . See Fig. 13F (J&W) also reproduced above. The cylindrical waves emerging from S 1 and S 2 are coherent, having been generated from the same original wave-front at S (comment on the concept of coherence in your report). These waves superimpose on the screen, labeled Σ, at a distance X from the plane defined by S 1 and S 2 . Thus, ( S 1 P ) 2 = X 2 + ( y- d/ 2) 2 . (1) ( S 2 P ) 2 = X 2 + ( y + d/ 2) 2 . (2) 1 ( S 2 P ) 2- ( S 1 P ) 2 = ( y + d/ 2) 2- ( y- d/ 2) 2 . (3) [( S 2 P ) + ( S 1 P )] * [( S 2 P )- ( S 1 P )] = 2yd . (4) ( S 2 P )- ( S 1 P ) = 2yd / [( S 2 P ) + ( S 1 P )] ≡ Δ , (5) Δ being defined as the path difference between the waves arriving at P. For X >> d , ( S 1 P ) + ( S 2 P ) ≈ 2 X. (6) Δ = yd /X. (7) This path difference results in a phase difference,...
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This note was uploaded on 12/09/2011 for the course PHYS 450 taught by Professor Staff during the Fall '08 term at Purdue.
- Fall '08