# OHW 34 - terry (ect328) – oldhomework 34 – Turner –...

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Unformatted text preview: terry (ect328) – oldhomework 34 – Turner – (59130) 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points The reflecting surfaces of two intersecting flat mirrors are at an angle of 66 ◦ , as shown in the figure. A light ray strikes the horizontal mirror at an angle of 48 ◦ with respect to the mirror’s surface. 66 ◦ 48 ◦ φ Figure is not drawn to scale. Calculate the angle φ . Correct answer: 48 ◦ . Explanation: Basic Concept: θ incident = θ reflected Solution: θ 1 θ 2 φ θ Figure is to scale. The sum of the angles in a triangle is 180 ◦ . In the triangle on the left we have angles θ , 180 ◦- θ 1 2 , and 180 ◦- θ 2 2 , so 180 ◦ = θ + 180 ◦- θ 1 2 + 180 ◦- θ 2 2 , or θ 1 + θ 2 = 2 θ . (1) In the triangle on the right we have angles θ 1 , θ 2 , and φ. 180 ◦ = θ 1 + θ 2 + φ, so θ 1 + θ 2 = 180 ◦- φ. (2) Combining Eq. 1 and 2, we have φ = 180 ◦- 2 θ = 180 ◦- 2 (66 ◦ ) = 48 ◦ . As a matter of interest, in the upper-half of the figure the angles (clockwise) in the triangles from left to right are 42 ◦ , 42 ◦ , and 96 ◦ ; 84 ◦ , 24 ◦ , and 72 ◦ ; 108 ◦ , 24 ◦ , and 48 ◦ ; 132 ◦ , 24 ◦ , and 24 ◦ ; and in the lower-half of the figure the angles (counter-clockwise) in the triangles from left to right are 24 ◦ , 24 ◦ , and 132 ◦ ; 48 ◦ , 24 ◦ , and 108 ◦ ; 72 ◦ , 42 ◦ , and 66 ◦ ; 114 ◦ , 42 ◦ , and 24 ◦ . 002 (part 1 of 2) 10.0 points Consider the case in which light ray A is in- cident on mirror 1 , as shown in the figure. The reflected ray is incident on mirror 2 and subsequently reflected as ray B. Let the an- gle of incidence (with respect to the normal) on mirror 1 be θ A = 55 ◦ and the point of incidence be located 20 cm from the edge of contact between the two mirrors. terry (ect328) – oldhomework 34 – Turner – (59130) 2 90 ◦ x A B mirror 1 mirror 2 θ A θ B What is the angle of the reflection of ray B (with respect to the normal) on mirror 2 ?...
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## This note was uploaded on 02/17/2010 for the course PHY 59130 taught by Professor Turner during the Fall '09 term at University of Texas.

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OHW 34 - terry (ect328) – oldhomework 34 – Turner –...

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