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Unformatted text preview: terry (ect328) – homework 39 – Turner – (59130) 1 This printout should have 10 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points A light ray is traveling in a medium with an index of refraction n 1 and it is reflected at the boundary of a second medium with an index of refraction n 2 . Considering the change of the relative phases Δ φ due to their reflections, which of the following conditions is correct? 1. If n 1 > n 2 , then Δ φ = 0 and if n 1 < n 2 , then Δ φ = π . correct 2. If n 1 > n 2 , then Δ φ = 0 and if n 1 < n 2 , then Δ φ = π 2 . 3. If n 1 > n 2 , then Δ φ = π 2 and if n 1 < n 2 , then Δ φ = π 2 . 4. If n 1 > n 2 , then Δ φ = 0 and if n 1 < n 2 , then Δ φ = 0. 5. If n 1 > n 2 , then Δ φ = π and if n 1 < n 2 , then Δ φ = π . 6. If n 1 > n 2 , then Δ φ = π 2 and if n 1 < n 2 , then Δ φ = π . Explanation: If a light ray is traveling in a medium with an index of refraction n 1 and it is reflected at the boundary of a second medium with an index of refraction n 2 , the phase change is Δ φ = 0 when n 1 > n 2 and is π when n 1 < n 2 . 002 (part 2 of 2) 10.0 points Consider the optical coating on a glass lens where the index of refraction of the coating is n , where n is greater than the index of refraction of the air. air lens t n θ θ ≈ ◦ 1 2 Assume: The index of refraction of the lens is greater than that of the coating. To minimize the reflection of a ray with a wavelength λ = 500 nm and incident angle θ ≈ 0, what is the minimum nonzero thickness t of the coating? 1. t = n λ 8 2. t = λ n 3. t = 3 n λ 4 4. t = 3 λ 4 n 5. t = λ 2 n 6. t = n λ 4 7. t = n λ 8. t = n λ 2 9. t = λ 4 n correct 10. t = λ 8 n Explanation: Destructive interference occurs when the difference between the phase angle of the inci dent ray reflected from the outer surface of the coating (ray 1) and the phase angle of the ray reflected from the inner surface of the coating (ray 2) are at π, 3 π, 5 π etc. The phase differ ences are due to the path difference of the two rays and the change of their relative phases due to reflections. Putting them together, itdue to reflections....
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 Fall '09
 Turner
 Light, Wavelength, Correct Answer, Terry

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