Diffraction occurs in water waves, sound waves, and light waves, but the amount of diffraction depends on the size of the obstacle or opening in relation to the wavelength of the wave. Wavelength dispersion (nm/mm) is non-linear varying as the diffraction angle and the distance to focus at each wavelength. In practice, wavelength dispersion is linear enough to present near constant resolution especially for low resolution instruments.
Diffraction And Dispersion Of Light Waves
Rays
Diffraction And Dispersion Of Light Energy
As we consider more phenomena associated with light, one of our primary concerns will be the direction that light is traveling. We already know that light, like any wave, travels in a direction perpendicular to its planes of constant phase:
- Dispersion, Diffraction and Diffraction Gratings. Because the refractive index depends on the wavelength, light of different colors (i.e., wavelengths).
- A simple explanation is that diffraction occurs when waves encounter obstacles (e.g. Pass through narrow openings), whereas dispersion occurs because the refractive index of a given medium is dependent upon wavelength (i.e. Different wavelengths travel at different speeds through that medium).
Figure 3.6.1 – Light Waves Travel in Several Directions at Once
So in our wave view of light, we say that the light wave is traveling in many directions at once, but now we are going to change our perspective to that of an observer and a source. When we do that, we narrow down all the possible directions of the light wave motion to a single line, which we call a light ray. This is a directed line that originates at the source of light, and ends at the observer of the light:
Apple tv screencast. Figure 3.6.2 – Source and Observer Define a Ray
Alert
Dispersion Of Light In Physics
When most people encounter the idea of a light ray for the first time, what they think of is a thinly-confined laser beam. This is not what is meant here! The ray has no physical meaning in terms of the confinement of light – we just use it as a simple geometrical device to link a source to an observer. Always keep in mind that the actual physical manifestation of the light is a wave that is usually traveling in many directions at once! Our use of rays will become so ubiquitous that this will be easy to forget.