Chapter27

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In 1801 an English scientist Thomas Young repeated the double slit experiment,but this time with light.S 1S 2Coherent light sourceΔlPEach slit acts like a coherent lightsource.The two waves meet at point P ona screen.Δl is the optical path difference ofthe two light waves coming fromS 1 and S 2 .The two waves interfere with eachother, and if:Δl = mλConstructive interference, and wesee a bright spot.ScreenΔl=( m + 1)λ2Destructive interference,and we see a dark spot.Thus, we should see alternating bright and dark regions (called fringes) as wemove along the screen and the above two conditions are satisfied.Can we find a relationship between the fringes and the wavelength of the light?The answer is yes……………
PAssume the screen is far away from theslits which are small. This is called theFraunhofer approximation.S 1θThus, since the slits are very closetogether, θ is the same for each ray.dS 2θΔlθFrom the figure we see that:sinθ=Δld⇒ Δl = d sinθScreenWe know that for constructive interference:Thus,d sinθ=mλd sinθ = ( m + 12)λΔl = mλfor constructive interference.and...for destructive interference.These are the interference conditions for the double slit.m is the order ofthe fringe.
Page 1 and 2: Algebra-based Physics IINov. 5 th :
Page 3 and 4: 27.1 The Principle of Linear Superp
Page 5: For interference to continue at som
Page 9 and 10: ExampleIn a Young’s double-slit e
Page 11 and 12: Double slit interferencedS 1S 2θΔ
Page 13 and 14: 27.3 Thin Film InterferenceLight wa
Page 15 and 16: So a phase shift can occur upon ref
Page 17 and 18: ⇒λ vac=(2)(375 nm)(1.33)m +12=99
Page 19 and 20: 27.5 DiffractionDiffraction is the
Page 21 and 22: We get more diffraction for the sit
Page 23 and 24: But, farther up the screen from the
Page 25 and 26: We have light passing thru openings
Page 27 and 28: Here is an image of two objects tha
Page 29 and 30: 27.7 The Diffraction GratingWe see
Page 31: diffraction pattern of a grating
Page 34 and 35: Indeed, a diffraction pattern does

Chapter27

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