How to Calculate the Width of a Slit for Diffraction Experiment?

What is the width of a slit for which the first minimum is at 45° when the slit is illuminated by a helium-neon laser (λ = 633 nm)? Answer: The width of the slit is 895 nm.

When conducting a diffraction experiment with a helium-neon laser with a wavelength of 633 nm, it is important to calculate the width of the slit to determine the angle at which the first minimum occurs.

To find the width of the slit, we can use the formula derived from Young's experiment, which relates the slit size to the wavelength of light and the order of fringes:

Formula:

sin(Q) = m * λ / d

Where:

  • Q = Angle of diffraction
  • m = Order of fringes
  • λ = Wavelength of light
  • d = Width of the slit

Given that the angle Q is 45 degrees and m is 1, we can find the width of the slit as follows:

Solution:

Using the formula above and substituting the values:

d = λ / sin(Q)

d = 633 * 10^-9 / sin(45)

d = 0.89 μm

Therefore, the width of the slit for the diffraction experiment with a helium-neon laser of wavelength 633 nm is approximately 895 nm.

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