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Homework Help: Problem help on optics

  1. Sep 13, 2004 #1
    Specifically, diffraction.. here are the insights of the problems...

    1. For a radio station operating at a frequency of 103.3 MHz has two identical dipole antennae 1000m apart, transmitting in a phase. At distances much greater than 1000m, at what angles is the intensity at a maximum?

    I believe I should use d sin 'theta' = m 'lambda' and find 'theta'.

    Here's my problem... I will only get the 'theta' by substitution of necessary value to the formula, but how will I find the angleS? What should I do with the formula? Make multiples of 1000m and m =2,3,...?

    2. Consider a straight black line drawn on a piece of white paper. After taking a film photo-graph of this arrangement, the resulting negative shows a thin, transparent line surrounded by opaque black. A laser, of 633 nm wavelength, strikes this negative, and the pattern is observed on a screen 60 m away. The distance between the central bright fringe and the first minimum(dark spot) is 32 mm. Determine the width of the slit on the negative.

    Insights: Can I use y = Rn 'lambda' / a where R is distance from slit to screen, y is distance between minima? So, the unknown is the 'a'.

    with 'lambda' = 633 nm; R = 60 m;

    Question: SHould my n be equal to 1? How about my y? 32mm.

    3. Coherent light from a mercury arc-discharge lamp is passed through a filter that blocks everything except for one spectral line in the green region of the spectrum. This light then falls on two slits separated by 600 mm. The resulting interference pattern is projected on a screen 2.5 mm away, and the adjacent bright lines are each separated by 5 mm. Determine the wavelength of the light used.
    y = Rn 'lambda' / a​
    My a is = 600mm, R = 2.5mm, 'lambda' is unknown... and y = 5mm? what should my n be?
  2. jcsd
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