Single-Slit Diffraction and Interference - Essay Example

Diffraction causes the phenomenon of Interference, which is defined as the diffraction pattern produced on a screen on the other side of the obstacle from the light source. Thus, when monochromatic light passes through a single slit, it flares out, producing a single-slit interference or diffraction pattern on the screen. The diffraction pattern has a bright central region, which is surrounded by symmetrically distributed less intense regions. These bright bands are the ‘maxima’ or areas of constructive interference, interspersed by the ‘minima’ or dark regions of destructive interference.

Thesis Statement: This paper will describe single-slit diffraction and interference. Single-Slit Diffraction and Interference A plane wave of light travels in a straight line; so when such a wave passes through a rectangular slit, one may expect it to fall on a distant screen in the form of a bright rectangle with sharp edges. However, the process of diffraction of light through the single-slit causes the interference or diffraction pattern formed on the screen to have blurred edges with faint lines of bright and dark, where some light has spread into the shadow.

The light wave spreading out from the slit is actually the interference effect termed as diffraction. As a result of diffraction, the light’s intensity is not uniform on the screen, and it extends into the shadow where it appears as secondary maxima. Between bright places in the shadow there are dark places termed intensity minima, where there is no light. According to Holbrow, Lloyd, Amato et al (2010), this is to be expected, taking a single slit of finite width b as two slits of width b/2 with no separation between them.

“There might be interference between the light wavefronts coming from these two different halves of the slit” (Holbrow et al 2010, p.313). By considering the slit of width b to be composed of narrower slits, the occurrence of the intensity minima of the Interference or diffraction pattern can be calculated. Serway and Vuille (2006) reiterate that slits cannot be assumed to have negligible widths acting as line sources of light. On the other hand, their non-zero widths form the basis for understanding the nature of the Fraunhofer Diffraction Pattern produced by a single slit.

Further, “according to Huygens’ principle, each portion of the slit acts as a source of waves” (Serway & Vuille 2006, p.638). A single slit diffraction pattern is formed when light passes through a single slit whose width w is on the order of the wavelength of the light. Huygen’s principle states that each part of the slit can be considered as an emitter of waves. “All these waves interfere to produce the diffraction pattern” (Physics, 2012). In the diagram (Fig.1) below is seen a slit of width w, through which light is passing through. Fig.1.

Single-Split Diffraction and Interference: Direction of the Light Wave (Physics, 2012) Destructive interference may occur between the ray at the top edge (ray 1) and the middle ray (ray 5). If so, the same occurs between rays 2 and 6, between 3 and 7, and b between 4 and 8. Thus, light from one-half of the single slit interferes destructively and cancels out light from the other half. “Ray 1 and ray 5 are half a wavelength out of phase if ray 5 must travel one-half wavelength further than ray 1” (Physics, 2012). Fig.2.

Single-Split Diffraction: Gradations in Light Intensity and Dark Areas (Physics,