Diffraction Pattern

Definition

A diffraction pattern is the distribution of light intensity that results when a wave, such as light or sound, encounters an aperture or obstacle. It is a fundamental phenomenon in wave physics that occurs when waves interact with a barrier or slit, causing the waves to bend and interfere with each other.

5 Must Know Facts For Your Next Test

1. The diffraction pattern of a single slit is characterized by a central bright fringe (maximum) surrounded by alternating bright and dark fringes (minima and maxima).
2. The width of the central bright fringe in a single slit diffraction pattern is inversely proportional to the width of the slit.
3. The positions of the minima in a single slit diffraction pattern are determined by the wavelength of the light and the width of the slit.
4. The intensity distribution in a diffraction pattern is governed by the principle of superposition, where the waves interfere constructively and destructively.
5. Diffraction patterns can be used to determine the wavelength of light or the size of an aperture or obstacle, as the pattern is sensitive to these parameters.

Review Questions

• Explain the formation of the diffraction pattern in a single slit experiment.
  • In a single slit diffraction experiment, the light waves passing through the slit spread out and interfere with each other. The resulting diffraction pattern consists of a central bright fringe (maximum) surrounded by alternating bright and dark fringes (minima and maxima). The width of the central bright fringe is inversely proportional to the width of the slit, while the positions of the minima are determined by the wavelength of the light and the slit width. This pattern is a result of the constructive and destructive interference of the light waves as they pass through the slit and spread out.
• Describe how the diffraction pattern changes as the slit width is varied.
  • As the width of the slit in a single slit diffraction experiment is decreased, the width of the central bright fringe in the diffraction pattern increases. Conversely, as the slit width is increased, the central bright fringe becomes narrower. This is because the diffraction pattern is inversely proportional to the slit width, as dictated by the principle of wave interference. The positions of the minima in the diffraction pattern are also affected by the slit width, with the minima occurring at different angular positions as the slit width is changed.
• Analyze the relationship between the wavelength of light and the diffraction pattern observed in a single slit experiment.
  • The wavelength of the light used in a single slit diffraction experiment is a crucial parameter that determines the characteristics of the diffraction pattern. As the wavelength of the light is increased, the positions of the minima in the diffraction pattern shift to larger angles, while the width of the central bright fringe decreases. This is because the positions of the minima are directly proportional to the wavelength and inversely proportional to the slit width. By observing the diffraction pattern and measuring the positions of the minima, one can determine the wavelength of the light used in the experiment, provided that the slit width is known.

Related terms

Interference: The interaction of waves, such as light or sound, resulting in a pattern of constructive and destructive interference.

Diffraction: The bending of waves around the edges of an obstacle or through an aperture, causing a spreading of the wave front.

Fraunhofer Diffraction: A type of diffraction pattern that occurs when the light source and the observation point are both far away from the aperture or obstacle, resulting in parallel incident and diffracted rays.