Homework Help Forum: Physics

Posted by Jimmy on Monday, January 26, 2009 at 7:00pm.

Problem 1 (5 Points) In the first application of interferometric methods in radio astronomy, Australian astronomers observed the interference between a radio wave arriving at their antenna directly from the Sun and on a path involving reflection from the surface of the sea. Assume that radio waves have a frequency of 6.0 ¡Á 107 Hz, and that the radio receiver is 25 m above the surface of the sea. What is the smallest angle ¦È above the horizon that will give destructive interference of the waves at the receiver? Problem 2 (8 Points) The figure to the right shows a Mach- Zehnder interferometer. Invented over 100 years ago, it is still used for many optical measurements. Light form a point source in the lower-left strikes a half-silvered mirror, which reflects half the light incident on it and transmits half the incident light. The two split beams, U and D, strike good mirrors which directs the rays to another half silvered mirror. This second half-silvered mirror splits the combined beams, directing half to detector 1 and the other half to detector 2. The detectors are indicated as half-circles. The device is constructed so that the light rays travel the same distance from where they are split by the 1st ¡°beam splitter¡± until they are combined at the 2nd one. What fraction of the light from the source enters detector 1? Problem 3 (4 Points) A converging lens has a focal length f, and a diverging lens has a focal length ¨Cf, which has the same magnitude as the converging lens. They are separated by a distance D which is greater than f, as shown. Parallel light enters from the left. Will the light be brought to a focus, and if so where? Problem 4 (3 Points) Imagine that the parallel light rays in Problem 3 enter from the right. Explain why the light will be brought to focus without using any equations.

• Physics - bobpursley, Monday, January 26, 2009 at 7:24pm

  I am not inclined to work these out for you.. Indicate your thinking in words, and I will critique. Reminder: on the first one, is there a phase shift upon reflection?

  
  

• Physics - Tdotjace, Wednesday, January 28, 2009 at 8:41pm

  Jimmy goes to uoft!

  
  

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