This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Platt, David Homework 35 Due: Dec 5 2005, 4:00 am Inst: Ken Shih 1 This printout should have 7 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. The due time is Central time. 001 (part 1 of 2) 10 points A material with an index of refraction of 1 . 15 is used to coat glass. The index of refraction of glass is 1 . 5. What is the minimum thickness of the coat ing that will minimize the reflection of light with a wavelength of 4730 A? Correct answer: 0 . 102826 m. Explanation: Basic Concepts: Phase Changes for Reflecting Waves. Solution: Since the coating has a refraction that is less than that for glass (but greater than that for air), we know that the reflected light from both the glass and the coating will undergo a 180 phase shift. This means that the to tal trip inside the coating must be exactly one half of the wavelength of light inside the coating . (Hence the waves reflected from the glass and from the coating will interfere de structively.) The wavelength of light inside the coating is n where n is the index of re fraction of the coating. This implies that the thickness of the coating must be one fourth the wavelength of light inside this medium. Hence (calling the thickness of the material t , the wavelength of light in air , and the index of refraction of the medium n ) t = 4 n = 4 . 73 10 7 m (4)(1 . 15) t = 1 . 02826 10 7 m = 0 . 102826 m ....
View
Full
Document
This note was uploaded on 04/10/2010 for the course PHY 317 taught by Professor Gositz during the Spring '08 term at University of Texas at Austin.
 Spring '08
 gositz

Click to edit the document details