Diffraction 1
What is diffraction?
- ability of waves to travel around corners and obstacles in their path
- ability of waves to spread out in wavefronts as they pass through a small aperture or a sharp edge
- diffraction occurs for both transverse and longitudinal waves
- amount of diffraction increases with increasing wavelength
- if a light beam is observed to have a high diffraction, it must have a high wavelength (low frequency)
- therefore amount diffraction can be used to analyse wavelengths
Further, this means that RED has a LOWER FREQUENCY than blue.
Huygens Principle
Explanation for Diffraction
Each point on a wave front can be considered to be a centre of disturbance for a new source of waves.
Important Notes
1. Narrower slits produce larger diffraction.2. If RED light is used: (red and black bands observed)
- fringes are more distinct
- broad central band of red light, with red and black bands
- red has a large wavelength and is diffracted a lot
- bands are wider
- red light is monochromatic : it is of single frequency
3.If BLUE light is used: (blue and black bands observed)
- fringes are more distinct
- broad central band of blue light, with blue and black bands
- blue has a smaller wavelength and is diffracted lesser
- therefore bands are narrower
- blue light is monochromatic : it is of single frequency