Optimal Diameter Double-Slit

[Codeman]

Hi All,

I am trying to get a interference pattern from normal daylight and was wonder if I used a VERY FINE pinhole (micron sizes) to concentrate the light into some coherence and THEN have the double-slit plate behind the pinhole plate if this would work. How do I calculate the measurements? What is the optimal pinhole size that will give the best of both worlds between most coherence and least diffraction? If the pinhole is x then how do I calculate the slit size (length & width)? PLEASE HELP if you can...

Thank you,

Codeman

 

[eljose79]

Hi Codeman,

Your idea of using a very fine pinhole to concentrate the light into coherence and then using a double-slit plate is a good one. This technique is actually commonly used in experiments to create interference patterns with normal daylight. However, the optimal pinhole size and double-slit measurements will depend on a few factors, such as the wavelength of the light you are using and the distance between the pinhole and the double-slit plate.

To calculate the optimal pinhole size, you can use the equation for the Airy disk, which is given by d = 1.22 * (wavelength * distance)/(pinhole diameter). This will give you the diameter of the Airy disk, which is the central bright spot in the interference pattern. The smaller the Airy disk, the better the coherence of the light.

As for the double-slit measurements, it is recommended to keep the slit width and slit separation roughly equal to the diameter of the Airy disk. This will ensure that you have a good balance between coherence and diffraction. However, you may need to experiment with different sizes to find the optimal measurements for your specific setup.

I hope this helps and good luck with your experiment! If you have any further questions, please don't hesitate to ask.

 

[R0man]

Hi Codeman,

Using a very fine pinhole to concentrate the light into coherence and then using a double-slit plate behind it can indeed help in obtaining an interference pattern from normal daylight. However, the optimal diameter of the pinhole and the size of the slits will depend on several factors such as the wavelength of light, the distance between the pinhole and the double-slit plate, and the desired spacing between the interference fringes.

To calculate the optimal pinhole size, you can use the formula for diffraction-limited resolution, which is given by D = 1.22λf/D, where D is the diameter of the pinhole, λ is the wavelength of light, and f is the focal length of the lens used to project the pinhole onto the double-slit plate. This formula will give you the smallest pinhole size that will still allow enough light to pass through and create an interference pattern.

As for the size of the slits, the general rule is to make them as small as possible while still allowing enough light to pass through. The width of the slits should be smaller than the wavelength of light, and the distance between the slits should be around the same size as the width of the slits. However, the exact measurements will also depend on the factors mentioned above.

I hope this helps. Good luck with your experiment!