1052_Physics ProblemsTechnical Physics

1052_Physics ProblemsTechnical Physics - Chapter 37 P37.33...

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Unformatted text preview: Chapter 37 P37.33 393 Treating the anti-reflectance coating like a camera-lens coating, FG H 2t = m + Let m = 0 : t= λ 4n = IJ K 1λ . 2n 3.00 cm = 0.500 cm . 4 1.50 af This anti-reflectance coating could be easily countered by changing the wavelength of the radar—to 1.50 cm—now creating maximum reflection! P37.34 FG H 2nt = m + IJ K 1 λ 2 so Minimum P37.35 FG 1 IJ λ H 2 K 2n F 1 I a500 nmf = t=G J H 2 K 2a1.30f t= m+ 96.2 nm . Since the light undergoes a 180° phase change at each surface of the film, the condition for 2nt . The film thickness is constructive interference is 2nt = mλ , or λ = m t = 1.00 × 10 −5 cm = 1.00 × 10 −7 m = 100 nm . Therefore, the wavelengths intensified in the reflected light are λ= a fa f 2 1.38 100 nm 276 nm where m = 1, 2 , 3 , … = m m or λ 1 = 276 nm , λ 2 = 138 nm , . . . . All reflection maxima are in the ultraviolet and beyond. No visible wavelengths are intensified. P37.36 (a) For maximum transmission, we want destructive interference in the light reflected from the front and back surfaces of the film. If the surrounding glass has refractive index greater than 1.378, light reflected from the front surface suffers no phase reversal and light reflected from the back does undergo phase reversal. This effect by itself would produce destructive interference, so we want the distance down and back to be one whole wavelength in the film: 2t = t= λ 2n = λ . n 656.3 nm = 238 nm 2 1.378 a f (b) The filter will expand. As t increases in 2nt = λ , so does λ increase . (c) Destructive interference for reflected light happens also for λ in 2nt = 2 λ , or P37.37 a f λ = 1.378 238 nm = 328 nm anear ultravioletf . If the path length difference ∆ = λ , the transmitted light will be bright. Since ∆ = 2d = λ , d min = λ 580 nm = = 290 nm . 2 2 ...
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .

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