Diffraction and Interference

If you look closely at the shadow cast by an opaque item close to the geometrical Shadow zone, you’ll notice that it has alternate dark and bright sections. This is due to the diffraction phenomenon. Whereas the phenomenon in which two light waves from two coherent sources superimposed each other to form a resultant wave of the high, low, or the same amplitude. The study of these two phenomena is really important as you will witness many of its applications in physics. When a wave comes across an obstacle diffraction occurs while if the waves superimpose each other then, interference occurs. The gap between separate fringes is non-uniform in diffraction. In the case of interference, however, the spacing between the fringes is uniform. In the case of diffraction, the least intensity locations are not fully dark. In the case of interference, however, the points of minimum intensity are completely dark.

Diffraction 

The spread of a light wave when it travels through a slit or any opaque object is known as diffraction. Diffraction is a phenomenon that happens in all waves. The phenomenon of waves colliding with an obstacle and the resulting bending around the obstacle is referred to as diffraction. Waves can also interfere in both constructive and destructive ways, resulting in a variety of wave patterns. Light bends in the same way around an object’s edge. Wavefronts travel through two minor openings in the animation. As they pass through the aperture, they visibly change direction or diffract. Example- Water waves bending around a fixed object are the most common example of diffraction.

Applications of diffraction you may witness in your daily life are- 

1. Holograms 
2. In the separation of white light 
3. From the shadow of an object 
4. X-ray diffraction
5. The reflection of rainbow colors in the CD is due to diffraction.

Interference 

When a light ray from two coherent sources traveling in the same medium superimposed each other it results in a phenomenon known as interference. We use Coherent sources for interference phenomena because they produce light waves with the same frequency and a constant phase difference. Interference is the collision and adding up of crests and troughs of two waves which results in dark and bright fringes is known as interference. The term “constructive interference” refers to when two waves collide to form a greater peak. Destructive interference occurs when waves collide to cancel one other out or form a wave with a lower height as a result. The resultant waveform for two waves in phase and out of phase is shown in the lower graphic. The in-phase waves are productively interfering, whereas the out-of-phase waves are destructively interfering.

The light reflected from a coating of oil floating on water is one of the best instances of interference. And the thin film of a soap bubble, which when illuminated by natural or artificial light sources reflects a rainbow of gorgeous hues. 

Difference between diffraction and interference 

Conclusion 

When a light wave passes through a small gap or slit, the phenomenon of light spreading occurs. It is known as diffraction whereas Interference refers to the act of superposition of multiple light waves whose emission takes place by two coherent sources. Diffraction occurs when light propagates through different parts of the same wavefront. Interference is the result of light emanating from two different wavefronts colliding. In the case of diffraction, the fringe width is not equal, whereas, in the case of interference, the fringe width is identical. The contrast between maxima and minima in diffraction is poor, but the contrast between maxima and minima in interference is good. A slit or obstacle is required for diffraction to occur, whereas there is no such necessity for wave interference. The direction of wave propagation is modified due to diffraction. The superposed wave in the case of interference, on the other hand, travels in the same direction.