8:26 AM physics.ryerson.ca iPad * 100% . Analyze below the diagram of a Michelso

Question

8:26 AM physics.ryerson.ca iPad * 100% . Analyze below the diagram of a Michelson interferometer. M2 BS CP If the semi-reflective surface of the beam splitter BS is the lower right how many times does the reflected wave R pass through the splitter? How many times does the transmitted wave T pass through the splitter? Thinking of your answers to questions 3a and 3b above can you justify the use of the compensator plate CP? a. b. c. When the movable mirror M2 is moved a distance d, a number N of fringes appear or disappear from the centre of the interference image on the screen E. Every time a fringe appears or disappears, M2 has been moved through a distance /2. Using this new information, can you justify the following equation by which the wavelength of the light can be calculated? 4. 2d

Explanation / Answer

The reflecting surface of the beam splitter is the lower right surface, the light ray reflecting at M2 passes through the BS three times, while the ray reflected at M1 travels through BS only once. The optical path length through the glass plate depends on its index of refraction, this gives a optical path difference between these two light rays. To compensate for this, a glass plate called CP of the same thickness and index of refraction as that of BS is introduced between M1 and BS so now light reflected at M1 also passes three times( first BS and two times from CP)

when we move half of the wave length, fringes appears or disappear. By moving moving M2 we can observe or count the number of fringes apperaing and diappering. so for N fringes if we need to move M2 by d distance we will actually walk N*lambda/2 distance.so d=N*lambda/2

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