Single-Slit Optical Diffraction Pattern and Profile Based on Cornu Spiral

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This is a simple but universal calculation of optical diffraction. With "pattern" selected, you can see well-known diffraction patterns. You can change the gap size of the slit, the screen position, and the wavelength of the light to be diffracted. These three parameters cover most situations of light diffraction by a single slit. When "profile" is selected, you can see the intensity plot according to the screen surface. When "clothoid" is selected, you can see the clothoid, also known as the Euler or Cornu spiral.

Contributed by: Yuji Oki (May 2015)
Open content licensed under CC BY-NC-SA



This Demonstration shows the light intensity pattern due to Fresnel diffraction by a narrow slit. The calculation is based on the Fresnel integrals and , with the intensity distribution on the screen given by , where is the wavelength of the light, is the slit width, and is the distance to the screen. This calculates the optical diffraction of the light that passes a single slit. The theory is based on the traditional Cornu spiral curve.

With the button "pattern" selected, you can vary the wavelength of light, the slit size, and the screen's position to cover any situation. Though this program is very close to the Demonstration "Single-Slit Diffraction Pattern," this version adds the variables "screen position" and "wavelength."

Select "profile" for the linear plot of the diffraction intensity.

Select "clothoid" to see a Cornu spiral and a corresponding red line to read out the diffraction intensity. Set "distance from light axes" to obtain the diffracted light intensity at the position on the screen.

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