Help with single slit diffraction (fraunhoffer)

[j-lee00]

Why( and how) does the intensity of the wave vary along a screen perpendicular to the optical axis?

 

[jtbell]

The light arriving at the screen is the superposition (sum) of waves from the various parts of the slit. In general, these waves each travel slightly different distances to reach a particular point on the screen, and so they interfere with each other. The amount of interference varies from one point to another on the screen.

Examples:

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/fraungeo.html#c1

One way to derive the formula that gives the intensity at various points on the screen:

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/sinint.html#c1

 

[astrokreng]

The intensity of the wave varies along a screen perpendicular to the optical axis in single slit diffraction because of the phenomenon known as diffraction. Diffraction occurs when a wave passes through an opening, in this case a single slit, and bends around the edges of the slit. This bending causes the wave to spread out, resulting in a pattern of bright and dark fringes on the screen.

The intensity of the wave is strongest at the center of the screen, where the direct beam of light passes through the slit without any interference. As the distance from the center increases, the intensity decreases due to interference between the diffracted waves. This interference can either be constructive, where the waves reinforce each other and create a brighter fringe, or destructive, where the waves cancel each other out and create a darker fringe.

The specific pattern of bright and dark fringes on the screen is determined by the wavelength of the wave, the size of the slit, and the distance between the slit and the screen. By studying this diffraction pattern, we can gain valuable information about the properties of the wave and the slit.

In order to understand the intensity variations along the screen, we use the Fraunhofer diffraction pattern, which applies to waves that are far enough away from the slit that they can be considered parallel. This allows us to use the simple equation for single slit diffraction, known as the diffraction equation, to calculate the intensity at any point on the screen.

In summary, the intensity of the wave varies along a screen perpendicular to the optical axis in single slit diffraction due to the phenomenon of diffraction and the interference between diffracted waves. By studying this intensity variation, we can gain a better understanding of the properties of the wave and the slit, and use this information to further our knowledge and research in the field of optics.