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27) (ex a only) In the Michelson interferoneter, an airtight chamber of length d is placed in path I of the light tram. Initially the chamtRr has air with index of refraction n. I , but slightly > I), and the light in the chamber has wavelength A. _ Then, we pump all air out of the chamber. The vacuum in the chamtRr now has index of refraction n, = I (exactly), and the light in tlw chamtRr has wavelength a) Write in ternwofonly , , and _ Explain. b) (i) In air. In terms of d and , find the numtRr N. of wavelengths along chamtRr length. (ii) In a vacuum: In terms of d and , find the numtRr Nv ofwavelengths along the chamtRr length. c) Circle your choice: