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Unformatted text preview: Name ___________________________________ Student ID ____________ Score_______ last first Physics 123C, Spring 09, Version D Exam 3, page 1 I. A thin layer of oil (n = 1 . 47) floats on a thick slab of glass (n = 1 . 67) as shown. The oil varies in thickness from 0 to 400 nm. Sunlight from directly overhead strikes the oil layer, and an observer looking straight down toward the glass sees only certain color(s) of reflected light. 1. (4 pts) Which choice best describes the color(s) of light that will be strongly reflected at the tip of the oil wedge (zero thickness)? A. Red colors ( λ ≈ 650 nm in air). B. Green colors ( λ ≈ 550 nm in air). C. Blue colors ( λ ≈ 450 nm in air). D. All colors will be strongly reflected (white reflection). E. No colors will be strongly reflected (darkness). 2. (5 pts) Suppose that only blue light ( λ = 450 nm in air) shines onto the oil wedge. Which choice best represents the number of different thicknesses (include zero at the tip) where this blue light is brightly reflected, considering the entire length of the oil wedge? A. Zero – no strong blue reflection anywhere along the wedge. B. One – there is one thickness that produces strong blue reflection. C. Two – there are two thicknesses that produce strong blue reflection. D. Three – there are 3 thicknesses that produce strong blue reflection. E. More than 3 – there are many thicknesses that strongly reflect blue light. 3. (5 pts) Which choice best represents a wavelength of visible light that would experience complete destructive interference where the oil thickness is 250 nm? 567 nm 490 nm 468 nm 430 nm More than one such wavelength A B C D E Useful Data: h = 6 . 63 × 10-34 J ∏ s 1.00 eV = 1 . 602 × 10-19 J Oil Glass Air This end 400 nm thick Name ___________________________________ Student ID ____________ Score_______ last first Physics 123C, Spring 09, Version D Exam 3, page 2 II. Matter Waves A beam of neutrons (rest mass 1 . 675 × 10-27 kg) of kinetic energy 9 . 00 × 10-16 J strikes a diffraction grating. Assume that the grating slits are very small (sub- atomic-sized) dimension in the horizontal width, but macroscopic (about 2 mm) in the vertical dimension....
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This note was uploaded on 06/07/2009 for the course PHYS 123 taught by Professor Boynton during the Spring '09 term at University of Washington.
- Spring '09