# Diffraction Of Light Through Single Slits

- Single Slit Diffraction Explained
- Single Slit Diffraction Equations
- Single Slit Diffraction Calculator
- Single Slit Diffraction

Diffraction by a Single Slit 3. The minima of the single-slit diffraction pattern occur when Diffraction by a Single Slit But when m=0, it’s the central maximum. Diffraction by a Single Slit Example: Single-slit diffraction maximum. Light of wavelength 750 nm passes through a slit 1.0 x 10-3 mm wide. Diffraction through a Single Slit Light passing through a single slit forms a diffraction pattern somewhat different from those formed by double slits or diffraction gratings, which we discussed in the chapter on interference. Figure 4.3 shows a single-slit diffraction pattern. A monochromatic light source is incident on the first screen which contains a slit. The emerging light then arrives at the second screen which has two parallel slits S S0 1and S2. Which serve as the sources of coherent light. The light waves emerging from the two slits then interfere and form an interference pattern on the viewing screen.

### Single Slit Diffraction Explained

This animated sketch shows the angle of the first order minima: the first minimum on either side of the central maximum. We call the slit width *a*, and we imagine it divided into two equal halves. Using the Huygens' construction, we consider a point at the very top of the slit, and another point a distance *a*/2 below it, *i.e.* a point at the very top of the lower half of the slit. Consider parallel rays from both points, at angle *θ* to the axis of symmetry. (Why parallel? Because the screen is distant. Typically in diffraction experiments, the slit is ~ 10 µm wide, while the distance to the screen might be ~ 1 m.)

The ray from the distance *a*/2 below has to travel an extra distance (*a* sin *θ*/2). If this distance is half a wavelength, *i.e*. if

*a*sin

*θ*=

*λ*

### Single Slit Diffraction Equations

### Single Slit Diffraction Calculator

then they are π/2 out of phase and they interfere destructively. Now, for every point in the top half of the slit, there is one in the bottom half a distance *a*/2 below and, at the angle that satisfies *a* sin *θ* = *λ*, they all interfere destructively.

### Single Slit Diffraction

So the first mimimum has sin *θ* = *λ*/*a*. On the other side of the axis of symmetry, sin *θ* = *–λ*/*a* is also a minimum. These two minima limit the broad central maximum.