What is the difference between interference and superposition

Ben Davis December 9, What is the difference between interference and superposition? What is the main difference between interference and diffraction? When two waves meet they combine according to the?

How do you find resultant waves? What is the resultant wave? When two waves are in same phase then the resultant wave is? When two waves combine via superposition we can find the resultant wave by? When two waves superimpose at a point the amplitude of the resultant wave 1 depends upon? We therefore need to take some time to develop the mathematics behind this effect.

We will do this within the same framework that we have been using — that of harmonic waves. When we look at the physical attributes of interference, what we will be examining is what happens to the intensity of the combined wave. For example, interference in sound will be exhibited in volume, and in light it will be brightness.

Both of these are measures of intensity. We need a reference point for intensity, and the one we will use is that of maximal constructive interference.

So what we seek is an equation that relates the intensity of two superposed, out-of-phase, but otherwise identical waves to the intensity we would see if they were in phase. That is, we want something that looks like this:. Note that this is four times the intensity of each individual wave , since the constructive interference adds the amplitudes which are equal — the waves are identical and the intensity is proportional to the square of the amplitude.

To find this function, we start with two wave functions that are identical except for their phases and superpose them:. Plug these into Equation 1. The phase difference between the two waves can be written in terms of the difference in position, time, and the phase constant, using Equation 1. Therefore the factor in Equation 1. The intensity is proportional to the square of the amplitude, so the intensity of this combined wave is:. The intensity of the out of phase combined wave is therefore:.

Notice that this relationship between total intensity and phase difference exactly matches the three criteria we outlined above. The sources are allowed to vibrate long enough for their respective waves to superpose. The amplitude of the combined wave is given by Equation 1. A simple form of wave interference is observed when two waves of the same frequency also called a plane wave intersect at an angle, as shown in.

Assuming the two waves are in phase at point B, then the relative phase changes along the x -axis. The phase difference at point A is given by:. Interference of Plane Waves : Geometrical arrangement for two plane wave interference.

Destructive interference occurs when the waves are half a cycle out of phase, or. Light exhibits wave characteristics in various media as well as in a vacuum. When light goes from a vacuum to some medium like water its speed and wavelength change, but its frequency f remains the same. When light is reflected off a medium with a higher index of refraction, crests get reflected as troughs and troughs get reflected as crests.

An air wedge is a simple interferometer used to visualize the disturbance of the wave front after propagation through a test object. An air wedge is one of the simplest designs of shearing interferometers used to visualize the disturbance of the wave front after propagation through a test object. An air wedge can be used with nearly any light source, including non-coherent white light. An example of an air wedge interferometer is shown in.

Air Wedge : Example of air wedge interferometer. The air gap between the two glass plates has two unique properties: it is very thin micrometer scale and has perfect flatness. Because of this extremely thin air-gap, the air wedge interferometer has been successfully used in experiments with femto-second high-power lasers. An incident beam of light encounters four boundaries at which the index of refraction of the media changes, causing four reflected beams or Fresnel reflections as shown in.

The first reflection occurs when the beam enters the first glass plate. The second reflection occurs when the beam exits the first plate and enters the air wedge, and the third reflection occurs when the beam exits the air wedge and enters the second glass plate. The fourth beam is reflected when it encounters the boundary of the second glass plate. The air wedge angle, between the second and third Fresnel reflections, can be adjusted, causing the reflected light beams to constructively and destructively interfere and create a fringe pattern.

To minimize image aberrations of the resulting fringes, the angle plane of the glass wedges has to be placed orthogonal to the angle plane of the air-wedge.