Difference between Diffraction and Interference

Waves are disturbances that travel through time and space while transferring energy. Periodic oscillations of a physical quantity, such as pressure, electric and magnetic fields, or displacement, are waves. The medium vibrates as the wave passes, but it does not move. Instead, the wave's energy is transferred from one point to another as it moves. Waves have two distinct properties: diffraction and interference.

1. Diffraction

The bending of waves around an obstacle or through an opening is known as diffraction. It occurs when a wave collides with an obstacle or a gap roughly the same size as its wavelength. The wave may spread out or interfere with itself. As a result, resulting in bright and dark areas. How light waves bend around the edges of an object is known as diffraction. For this reason, even when there isn't a clear line of sight, you can see around corners. When light travels through a small opening, like a camera's aperture or a diffraction grating's slits, diffraction can also happen.

Diffraction of light

Diffraction is not limited only to light waves; it can also occur with sound and water waves. Diffraction can be seen in many everyday situations, such as how sound waves bend around corners or how water waves spread out as they pass through a gap in a breakwater.

If the obstacle or gap is much smaller than the wavelength, the wave will not diffract much and will pass through. If the obstacle or gap is much larger than the wavelength, the wave will diffract, but only slightly.

Diffraction occurs only when the size of the obstacle/aperture is comparable to the wavelength of the light used. The greater the wavelength, the more pronounced the diffraction effect. It is due to this reason that the diffraction effect is very commonly observed in sound.

However, suppose the obstacle or gap is approximately the same size as the wave's wavelength. In that case, the wave will diffract significantly and may interfere with itself, resulting in bright and dark areas. The diffraction pattern is determined by the shape of the obstacle or gap and the incoming wave's direction.

Diffraction is an important phenomenon with many practical applications, such as in the design of antennas, optical fibers, and lenses. It is also a key factor in diffraction grating (a device used to disperse light into its component wavelengths).

Factors Affecting Diffraction

1. Wavelength: The amount of diffraction is directly proportional to wavelength. So, the longer the wavelength, the more the diffraction, and vice versa.
2. Dimensions of the obstacle or gap: The amount of diffraction that occurs is also affected by the size of the obstacle or gap. The wave will not diffract significantly if the obstacle or gap is smaller than the wavelength. The wave will diffract if the obstacle or gap is much larger than the wavelength, but the amount of diffraction will be small.
3. The angle of incidence: The angle at which the wave strikes the obstacle or gap influences the amount of diffraction. The diffraction is greatest when the wave strikes the obstacle or gap at a perpendicular angle.
4. The shape of the obstacle or gap: The shape of the obstacle or gap can also influence the diffraction pattern. A circular obstacle, for example, will produce a different diffraction pattern than a square obstacle of the same size. The shape of an obstacle or gap can significantly impact a wave's diffraction pattern. Consider light diffraction through a single narrow slit; the diffraction pattern will be a series of concentric rings if the slit is circular. The diffraction pattern will be a series of parallel stripes if the slit is rectangular. The diffraction pattern gives straight stipes when an obstacle is a straight edge, like a sharp object and when the observation plane is at a right angle to the edge of a sharp surface

In general, the number, shape, and size of the diffraction maxima and minima produced are determined by the shape of the obstacle or gap. A circular aperture, for example, will produce a diffraction pattern with a single central maximum, whereas a rectangular aperture will not.

1. Wave frequency: The higher the wave's frequency, the less it will diffract.
2. Wave polarization: The polarization of the wave can also affect diffraction. Light waves which are parallel to a slit diffract differently than light waves perpendicular to the slit.
3. The geometry of the system: The diffraction pattern produced by a circular aperture, for example, will differ from the diffraction pattern produced by a rectangular aperture.
4. Presence of other waves: The presence of other waves can interfere with a given wave's diffraction pattern. The diffraction pattern of a light wave passing through a grating.

2. Interference

Interference between two waves occurs when two waves collide at the same location and time, which can result in the waves reinforcing each other, with the combined wave having a larger amplitude than either individual wave, or the waves canceling each other out, with the combined wave having a smaller amplitude than either individual wave.

Interference of light

Interference is classified into two types: constructive interference and destructive interference.

i) Constructive Interference:

It occurs when the two waves are in phase, meaning their peaks and troughs coincide. As a result, the combined wave is larger in amplitude than either of the individual waves. Constructive interference is a type of interference that occurs when two waves overlap in such a way that their peaks and troughs coincide. As a result, the combined wave is larger in amplitude than either of the individual waves.

• Constructive interference can occur only when the frequencies and amplitudes of the two interfering waves are the same. If the waves are not perfectly aligned, the resulting interference pattern will be more complex, containing both constructive and destructive interference.
• Many wave properties, such as diffraction, refraction, and polarization, are caused by constructive interference. These phenomena are all related to how waves interact with one another and with various materials.
• In telecommunications and other applications, constructive interference can amplify signals. When two antennas are placed so that their signals reinforce each other, the combined signal is stronger than either of the individual signals.
• Many scientific and engineering applications rely on constructive interference. Constructive interference, for example, can be used in acoustics to generate sound waves with a very specific pattern of peaks and troughs, which can then be used to generate standing waves in tubes or other structures.
• Constructive interference is a fundamental concept in wave theory that is required to comprehend many of the properties of waves and their interactions.

ii) Destructive Interference:

When two waves are out of phase, the peaks of one coincide with the troughs of the other, and destructive interference occurs. It results in a combined wave with a smaller amplitude than either of the individual waves and in some cases, the waves are completely canceled.

Destructive interference can be seen in a variety of circumstances. If two speakers are placed at opposite ends of a room and play the same sound wave at the same frequency and amplitude, the waves will overlap and create an annoying sound. It occurs when two waves collide and cancel each other out. This can occur when two waves are in phase, i.e., their peaks and troughs are aligned, or when they are out of phase, i.e., their peaks and troughs are not aligned. The resulting wave has a smaller amplitude, or height, than the original waves in both cases.

Consider two people standing at opposite ends of a diving board, waving their arms up and down. If the people are in phase, which means they both start waving simultaneously and continue to do so, the waves created by their arms cancel each other out, and the diving board remains still. If the people are out of phase, one person begins waving before the other, and the waves will cancel each other out, but the diving board will still move slightly as the waves interact.

Destructive interference has several practical applications. It is used in noise-canceling headphones, which use microphones to detect ambient noise and generate an out-of-phase wave with the noise, resulting in a quieter listening experience. It is also used in radar systems, which rely on the ability to detect small changes in a radio wave's reflection as it bounces off an object. Radar systems can detect even minor changes in the reflected wave by using destructive interference to cancel out the original wave, allowing them to locate and track objects accurately.

• Destructive interference occurs when two waves are out of phase, meaning they are not aligned in time. When two waves are out of phase, the crest of one wave coincides with the trough of the other wave, causing their amplitudes to cancel each other out.
• Destructive interference can occur in any type of wave, including sound waves, electromagnetic waves, and water waves.
• In addition to canceling out the amplitudes of the two waves, destructive interference can also cause the system's total energy to decrease.
• Destructive interference can be used to produce patterns of constructive and destructive interference known as interference patterns. These patterns can be observed in many contexts, including the double-slit experiment in physics and the patterns formed by sound waves reflecting off a wall.
• Destructive interference can filter out certain frequencies or wavelengths of a wave. For example, a resonator can filter out all frequencies except for a narrow band of frequencies, allowing only those frequencies to pass through.