E. Wave Nature of Light
2 Competing Theories:
Behavior of Light Supporting Wave Theory
1. Diffraction – light spreads out into the region behind an obstacle
What kind of wave behavior is demonstrated below?
2. Interference – Young’s Double Slit - Late 1800's
Which light source is coherent?
If you draw a line from each slit to the 1st order bright line, you will notice that one line is longer than the other.
The difference between these two lines is 1λ.
q = angle between slits and line
d = distance between slits
m = 0, 1, 2, .... order bright lines
m = 1/2, 1 1/2, 2 1/2 dark lines
q = angle to bright line
x/L = ml/d
x = distance from central maxima
Ex) Calculate the distance between two slits in a Double Slit Experiment if the wavelength of the light used is is 5 x 10-7 m and the distance between the central maximum and the first order bright line is 2 x 10-2 m. The distance from the slits to the screen is 4 meters.
Question: If they give you d, L and x and asked you to find the COLOR of the light used, What would you do? Where would you go to find the color?
1. Solve for λ use Young's Equation
2. Use 3 x 108 m/s = fλ to find the colors frequency
3. Look up the color on page 2 Ref.
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