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Measuring Planck's Constant Sitting at Your Desk (25 pts)

In this problem, you will use the ``night-time speckle effect'' and then use that effect to make an arm-chair estimate of the value of Planck's constant h.

When we observe objects at low illuminations we see ``static'' similar to what one might see on a television set. In this question we investigate the issue of whether this might be due to the randomness in the arrival of photons, so called ``photon shot noise.''

We will use the following rough observations about the human eye, which you could make yourself.

  1. The ``response/sampling'' time for the human eye is somewhere between the imperceptible cycle time of fluorescent lighting and the noticeable flicker of old-time movies at 15 frames per second, tex2html_wrap_inline438
  2. The resolution of the human eye is tex2html_wrap_inline440 (the angle of a single pixel on a tex2html_wrap_inline442 CRT at a viewing distance about 30 cm). This corresponds to a solid viewing angle of each receptor of about tex2html_wrap_inline446 st. rad.
  3. The radius of the pupil (the aperture through which light enters the eye) is 0.4 cm making the total area over which it gathers light tex2html_wrap_inline450
  4. The human eye can perceive fluctuations in brightness on the order of about f=3% of the power received. (8 bits is more than enough to digitally encode black and white pictures.)





Prof. Tomas Alberto Arias
Thu Feb 6 11:34:49 EST 1997