This picture represents the effects of different wavelengths of light with a diffraction grating. Using a green laser of wavelength 532 nm, a red laser of wavelength 670 nm, and diffraction grating of 600 lines/cm, an interference pattern was produced. In order to view the interference pattern, a smoke machine was used to produce neutrally buoyant reflective gas to make the light beams visible for the camera. The physics involved in the image demonstrates the dependence of diffraction pattern on wavelength where dsin theta = m lambda, where d is the separation of slits, theta is the angular spacing between maxima, m is the order of maxima and lambda is the wavelength. Given the red laser’s longer wavelength than the green laser, angle theta between the maxima and the central maximum is larger, for the red. This is clearly shown by the numerous green maxima occurring between adjacent red maxima. Note the violet laser of wavelength, 405 nm, is also used but the low intensity of reflected maxima prevents photography.

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Blago Hristovski and Jim Strachan, Physics Teacher
Kelowna Secondary School, Kelowna, British Columbia
Second Prize ( High School Individual Category )

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