1 Answer
Diffraction refers to the bending or spreading of waves, such as light, sound, or water waves, when they encounter obstacles or pass through narrow openings. There are two main types of diffraction based on the situation in which the wave interacts with objects:
1. Fresnel Diffraction
- Occurs when the source of the wave or the observation point is at a finite distance from the obstacle or aperture.
- This type of diffraction typically happens when the wave doesn't fully "fill" the space around the obstacle, and the curvature of the wavefront is important.
- It involves complex calculations and is usually observed in situations with short distances between the source, aperture, and screen (e.g., looking at a shadow cast by a small object close to the light source).
Example: When light passes through a small slit and forms patterns of bright and dark spots on a screen placed nearby.
2. Fraunhofer Diffraction
- Occurs when the source of the wave and the observation point are at an infinite distance from the obstacle or aperture.
- In this case, the waves are considered to be parallel, and the diffraction pattern can be analyzed as if the waves are traveling in straight lines.
- This type of diffraction is simpler to study and is commonly observed in laboratory experiments, where the wave is considered to be planar, and the observation screen is far from the diffracting object.
Example: Diffraction of light from a single slit or diffraction grating when viewed from a far distance.
Key Differences:
Both types of diffraction can create patterns of constructive and destructive interference (light and dark bands), but they apply in different physical setups.
1. Fresnel Diffraction
- Occurs when the source of the wave or the observation point is at a finite distance from the obstacle or aperture.- This type of diffraction typically happens when the wave doesn't fully "fill" the space around the obstacle, and the curvature of the wavefront is important.
- It involves complex calculations and is usually observed in situations with short distances between the source, aperture, and screen (e.g., looking at a shadow cast by a small object close to the light source).
Example: When light passes through a small slit and forms patterns of bright and dark spots on a screen placed nearby.
2. Fraunhofer Diffraction
- Occurs when the source of the wave and the observation point are at an infinite distance from the obstacle or aperture.- In this case, the waves are considered to be parallel, and the diffraction pattern can be analyzed as if the waves are traveling in straight lines.
- This type of diffraction is simpler to study and is commonly observed in laboratory experiments, where the wave is considered to be planar, and the observation screen is far from the diffracting object.
Example: Diffraction of light from a single slit or diffraction grating when viewed from a far distance.
Key Differences:
- Fresnel Diffraction: More complex, near-field diffraction.
- Fraunhofer Diffraction: Simplified, far-field diffraction (usually with parallel rays).
Both types of diffraction can create patterns of constructive and destructive interference (light and dark bands), but they apply in different physical setups.