Careers360 Logo
Scan and Download the App!
Search Faster,
Smarter, Better
Rated 4.2
by 1M+ students
Coherent Sources - Definition, Example, Types, FAQs

Coherent Sources - Definition, Example, Types, FAQs

Edited By Vishal kumar | Updated on Jul 02, 2025 04:25 PM IST

What are Coherent Sources of light?

If the sources have zero or continuous phase differences with the same quantity, then those two sources are junctions. Most of the surrounding light sources such as a bulb, sun, candle, etc. are a combination of several unconnected light sources. With parallel sources, the laser is a model, that is, many important sources within the laser are locked in stages. Two coherent sources of light can be obtained when they have exactly the same frequency and have zero phase difference.

This Story also Contains
  1. What are Coherent Sources of light?
  2. Coherent Sources Example
  3. What is Disruption?
  4. Application of interference of coherent sources
Coherent Sources - Definition, Example, Types, FAQs
Coherent Sources - Definition, Example, Types, FAQs

Coherent sources of light Definition

To see the effects of certain visual conditions such as board disturbances, you will need compatible light sources. Two equal slits illuminated by a laser beam can be said to be two sources of parallel points.

In addition, two light sources are said to combine to produce the same light coherent waves

  • Category and size
  • Wavelength and phase variability
  • Wavelength and intensity
  • Speed and phase
Background wave

Also read -

Coherent Sources Example

An example of a coherent light source is laser light. The light emitted by the laser has the same phase and frequency.

Another example of related sources is sound coherent waves. In the same difficulty and phase, electric signals travel from sound coherent waves.

Interference of light Examples:

One of the best examples of interference is demonstrated by the light reflected from a film of oil floating on water

What is Disruption?

Disruption occurs when two or more coherent waves of the same length and length meet.

Depending on the basis of wave propagation, when several wave disturbances pass a given area, the effect of the current effect is the amount of disturbance due to individual coherent waves.

Definition of Light Disruption

When two wavelengths of light are combined from different sources, the distribution of energy by a single wave is interrupted by another. This change in light distribution is called light disturbance, due to the resistance of two light coherent waves.

Types of Disruptions

Constructive disturbances and destructive disturbances are two types of light interference coherent waves depending on the colliding coherent waves.

Wave disruption: In this case, rhinos and the formation of both coherent waves will be formed to form a wave of equal size. The total volume of both coherent waves is known as the Construction Interference.

Disruptive Disruption: When both bumps collide in such a way that the split of the first wave collides with the second wave and the first wave collides with the second wave. After that, the ark and the crashing of both coherent waves will collide to form a wave.

The wavelength created will be equal to the difference in the width of both coherent waves. If the magnitude of the two coherent waves is the same, and after the disturbance, the amplitude is zero, this is known as the Destruction Interference.

NEET Highest Scoring Chapters & Topics
This ebook serves as a valuable study guide for NEET exams, specifically designed to assist students in light of recent changes and the removal of certain topics from the NEET exam.
Download E-book

How Can You Produce Coherent Resources?

Ways to produce coherent sources

Here are some ways to produce a consistent light source.

a. By splitting Wavefront

The front area can be divided into several sections. Can be applied using different lenses, glasses, and prisms are Young's double experiments, Lloyd's mirror layout, and Fresnel's way of flipping through other techniques.

b. By Dividing the Width

If the size of the incoming beam of light is separated, then a corresponding source can be formed. This can be done through a partial display or retrieval process. These separated parts continue to combine to create disruption.

Application of interference of coherent sources

Radiography is a technique that uses next-generation beam joints and makes it easy to cross a common barrier easily.

X-ray beam contains:

a)High surface area - In this case, the size and variability of the pole is small

b)Good temporary interaction - Occurs after monochromatization.

These poles are the result of their brilliance. Allows new techniques to be developed in the X-ray field:

Phase comparisons, tomography, and imaging

Photon correlation spectroscopy

NCERT Physics Notes :

On-line holography.

Integration is also the basis for other applications of interference of coherent sources of interference of coherent sources. Some of the applications of interference of coherent sources of interference of coherent sources are listed below:

i. Holography

It uses a coherent combination of optical coherent waves, and its use is often found on credit cards.

ii. Non-optical Wavefield

Elevation of optical wave fields is also possible, as opposed to holography. For example, the field of probability related to wave function is considered in quantum mechanics. Compatible coherent waves also have the application of interference of coherent sources of interference of coherent sources in future technologies such as quantum computing.

iii. Modal Review

Compatibility is used for model analysis to maintain the quality of the transfer function.

Also, check-

Frequently Asked Questions (FAQs)

1. What Is Sustained Interference and condition for sustained interference when interference of light takes place?

Interference of light definition: Interference models that correspond to areas of greater and less time are called continuous or permanent intervention patterns.

The conditions for interference for the implementation of the ongoing disruption can be stated as:

The two sources must be compatible

Two sources should be very small

Sources should be close together to form distinct and open edges.

Short-term continuous interference means continuous interference of light is evidence that (caused by random variance).

A concomitant source of monochromatic light (single wavelength) is required for two-dimensional experiments.

The idea is that you need a continuous phase interaction between light rays in order to detect a continuous disturbance pattern.

2. What are coherent sources of Sustainable Disorders?

All EM coherent waves form disruptive patterns. Integrated sources create static patterns that can be easily explored. A laser is an obvious solution usually if you wish to have a visible light source. At some wavelengths, the radio feeds multiple antennas far causing similar interference patterns at a much higher rate.

3. What Are the Conditions of Light Disturbance?

There are the following conditions for light wave interference: the wave source must be constant, emitting the same coherent waves and continuous phase difference. The wave must be monochromatic - it must be the same length.

Also, for further disruption, the following conditions are required:

Compatible light sources

The power and amplitudes must be approximately equal to produce a sufficient difference between the minimum and the maximum.

In order to be considered a point light source, the source must be small enough.

To produce wide edges, disturbing sources must be close to each other

To produce wide edges, the distance between screen and source and screen must be large

Sources should reflect light in the same state of separation.

Sources should be the same length.

4. What Are the Situations of Constructive Distress?

These are:

 Many coherent waves have to go together,

Most coherent waves have to be the same length, too

The coherent waves have to be separated. Some say that the light should be the same but that the disturbance only occurs with the corresponding light.

5. Is the Sun the coherent sources?

The sun is usually an inexhaustible source of light. However, sunlight can transmit a contact dot to a microscope image. Many luminous sources concern the spatial interaction (relative to angular size) and temporal interaction (relative to wavelength).

6. Can Two Independent Sources Join?

No, the two independent sources of light will never come together. When individual atoms return to earth, light is released. Even the smallest source of light cannot produce the same amount of light.

7. Why are coherent sources important in wave optics experiments?
Coherent sources are crucial for observing and studying interference and diffraction phenomena. They allow for the creation of stable, predictable interference patterns, which are essential for many optical experiments and applications.
8. How does a laser produce coherent light?
Lasers produce coherent light through a process called stimulated emission. This involves exciting atoms to higher energy states and then stimulating them to emit photons with the same frequency and phase, resulting in a beam of coherent light.
9. What is the role of coherent sources in holography?
Coherent sources are essential in holography for creating and reconstructing holograms. They provide the stable interference patterns needed to record the complex wavefront information of an object and later reproduce a 3D image.
10. What is temporal coherence?
Temporal coherence refers to the correlation between the phases of a light wave at different points in time. A light source with high temporal coherence maintains its phase relationship for a longer time, producing a more extended coherence length.
11. What is the significance of coherence time in optics?
Coherence time is the duration over which a light wave maintains a predictable phase relationship with itself. It's inversely proportional to the spectral bandwidth of the light source and determines the coherence length.
12. What is an example of a coherent light source?
A laser is an excellent example of a coherent light source. Lasers emit light waves with the same frequency and phase, making them ideal for experiments and applications requiring coherent light.
13. Can two independent lasers be considered coherent sources?
Generally, no. Even if two lasers emit light at the same frequency, they are unlikely to maintain a constant phase relationship over time. To be considered coherent sources, they would need to be phase-locked or derived from the same original source.
14. How do you create two coherent sources from a single source?
Two common methods are:
15. Can partially coherent sources produce interference patterns?
Yes, partially coherent sources can produce interference patterns, but these patterns will have reduced contrast and visibility compared to those produced by fully coherent sources.
16. How does the size of a light source affect its spatial coherence?
Generally, smaller light sources have higher spatial coherence. A point source, being the smallest possible source, has perfect spatial coherence across its wavefront.
17. What are coherent sources in wave optics?
Coherent sources are two or more sources of light waves that maintain a constant phase relationship over time. This means the waves from these sources have the same frequency and a fixed phase difference, allowing them to produce stable interference patterns.
18. How do coherent sources differ from incoherent sources?
Coherent sources maintain a constant phase relationship, while incoherent sources have random phase relationships. Coherent sources produce stable interference patterns, whereas incoherent sources do not create consistent interference effects.
19. Can natural light sources be considered coherent?
Generally, no. Natural light sources like the sun or a light bulb are typically incoherent because they emit light with random phase relationships. Coherent sources usually require special techniques or devices to produce.
20. What is spatial coherence?
Spatial coherence describes the correlation between the phases of light waves at different points in space perpendicular to the direction of propagation. High spatial coherence means the wavefront remains more uniform over a larger area.
21. How does the wavelength of light affect coherence?
The wavelength of light doesn't directly affect coherence. However, sources emitting a narrow range of wavelengths (monochromatic light) tend to have higher temporal coherence than those emitting a broad spectrum.
22. How does atmospheric turbulence affect the coherence of light from distant stars?
Atmospheric turbulence can reduce the spatial coherence of starlight. It causes random phase fluctuations across the wavefront, leading to phenomena like stellar scintillation (twinkling) and limiting the resolution of ground-based telescopes.
23. How does coherence length relate to temporal coherence?
Coherence length is directly related to temporal coherence. It represents the maximum path difference over which interference effects can be observed. A longer coherence length indicates higher temporal coherence.
24. What is the coherence function in optics?
The coherence function is a mathematical description of the degree of coherence between two points in a wave field. It quantifies how well correlated the phases of the waves are at these points.
25. Can coherent sources be used to generate entangled photons?
Yes, coherent sources, particularly lasers, are often used in the process of generating entangled photons through methods like spontaneous parametric down-conversion (SPDC). The coherence of the pump beam is crucial for this quantum optical phenomenon.
26. What is meant by "coherent backscattering"?
Coherent backscattering is a phenomenon where waves traveling along time-reversed paths in a disordered medium interfere constructively in the backward direction. It leads to enhanced backscattering and is observed with coherent light sources in materials like clouds or powders.
27. How does coherence affect the resolution of a microscope?
Higher spatial coherence can improve the resolution of a microscope by allowing for better focusing and reducing background noise. However, excessive coherence can also lead to unwanted interference effects, so a balance is often needed for optimal imaging.
28. What is the role of coherence in quantum computing with photons?
Coherence is crucial in photonic quantum computing as it allows for the maintenance of quantum superposition states and the implementation of quantum gates. Coherent manipulation of photon states is essential for quantum information processing.
29. What is the role of coherence in quantum metrology?
Coherence plays a crucial role in quantum metrology by enabling quantum superposition and entanglement. These quantum properties allow for measurements with precision beyond the standard quantum limit, leading to enhanced sensing and measurement capabilities in various fields.
30. What is the difference between longitudinal and transverse coherence?
Longitudinal coherence refers to the coherence along the direction of wave propagation (related to temporal coherence), while transverse coherence refers to coherence perpendicular to the propagation direction (related to spatial coherence).
31. Can coherent sources have different amplitudes?
Yes, coherent sources can have different amplitudes while still maintaining a constant phase relationship. The amplitude difference will affect the intensity of the interference pattern but not its stability.
32. How does coherence affect the visibility of interference fringes?
Higher coherence leads to greater visibility of interference fringes. As coherence decreases, the contrast between bright and dark fringes reduces, eventually leading to the disappearance of the interference pattern.
33. What is a coherence area?
A coherence area is the region over which a wavefront maintains a high degree of spatial coherence. Within this area, the wave's phase is highly correlated, allowing for clear interference effects.
34. How do coherent sources contribute to the formation of standing waves?
Coherent sources with opposite phases can create standing waves when their waves superpose. The constant phase relationship ensures that nodes and antinodes remain fixed in space, forming a stable standing wave pattern.
35. Can coherent sources be used to measure small displacements?
Yes, coherent sources are used in interferometry to measure extremely small displacements. By observing changes in the interference pattern, displacements on the order of a fraction of a wavelength can be detected.
36. What is the relationship between coherence and monochromaticity?
While not exactly the same, monochromaticity (single wavelength) often implies high temporal coherence. Monochromatic sources tend to have longer coherence lengths, but coherence also depends on the phase stability of the source.
37. What is a coherence volume?
A coherence volume is the three-dimensional region within which the light waves maintain a high degree of both spatial and temporal coherence. It's essentially the product of the coherence area and the coherence length.
38. How do coherent sources enable phase-shifting interferometry?
Coherent sources allow for precise control of the phase difference between interfering waves. In phase-shifting interferometry, this property is used to introduce known phase shifts, enabling high-precision measurements of surface profiles and optical properties.
39. What is the significance of coherent sources in fiber optic communications?
Coherent sources, especially lasers, are essential in fiber optic communications. They provide the narrow-bandwidth, high-intensity light needed for long-distance transmission and enable advanced modulation techniques for increased data capacity.
40. How does the coherence of a source affect its ability to focus?
Higher coherence allows for better focusing of light. Spatially coherent sources can be focused to smaller spot sizes, limited only by diffraction, while less coherent sources have larger minimum spot sizes due to their spatial phase variations.
41. How do coherent sources enable holographic data storage?
Coherent sources allow for the creation of complex, stable interference patterns that can encode large amounts of data in a holographic medium. The coherence ensures that the stored information can be accurately retrieved through reconstruction of the hologram.
42. What is the role of coherent sources in optical coherence tomography (OCT)?
In OCT, coherent sources (often low-coherence sources) are used to create cross-sectional images of tissues. The coherence properties of the light source determine the axial resolution of the imaging system.
43. How does coherence affect the operation of a Michelson interferometer?
The coherence of the light source determines the maximum path difference over which interference fringes can be observed in a Michelson interferometer. Higher coherence allows for the measurement of larger path differences and more precise interferometric measurements.
44. Can coherent sources be used to generate squeezed states of light?
Yes, coherent sources, particularly lasers, are used to generate squeezed states of light. These non-classical states of light have reduced quantum noise in one quadrature at the expense of increased noise in the other, and they rely on the coherent properties of the input light.
45. What is coherent population trapping in atomic physics?
Coherent population trapping is a quantum interference effect where atoms are trapped in a non-absorbing state through the interaction with two coherent light fields. This phenomenon relies on the phase relationship between the light fields and the atomic states.
46. How do coherent sources enable the creation of optical lattices?
Coherent sources, typically lasers, are used to create optical lattices by forming standing wave patterns through interference. The coherence of the sources ensures stable, well-defined potential wells for trapping and manipulating atoms or particles.
47. What is the difference between first-order and second-order coherence?
First-order coherence refers to the correlation of the electric field amplitudes and is related to the ability to form interference patterns. Second-order coherence describes the correlation of intensities and is related to photon statistics and quantum properties of light.
48. What is coherent anti-Stokes Raman spectroscopy (CARS)?
CARS is a spectroscopic technique that uses multiple coherent light sources to probe molecular vibrations. It relies on the coherent interaction of light fields with the sample to generate a signal at the anti-Stokes frequency, providing high-sensitivity chemical analysis.
49. How do coherent sources enable the creation of optical frequency combs?
Optical frequency combs are generated using ultra-short pulse lasers, which are highly coherent sources. The coherence of the laser allows for the generation of a stable, equally spaced set of frequency components, forming the "teeth" of the frequency comb.
50. How does coherence affect the operation of a laser gyroscope?
In a laser gyroscope, the coherence of the laser light is essential for detecting small phase shifts caused by rotation. The high coherence allows for precise measurement of the interference between counter-propagating beams, enabling accurate rotation sensing.
51. What is coherent perfect absorption?
Coherent perfect absorption is a phenomenon where all incident light is absorbed by a material when the incident waves are coherent and have specific phase relationships. It relies on the interference between incident and scattered waves to eliminate reflection and transmission.
52. How do coherent sources enable the study of quantum walks?
Coherent sources, particularly in the form of single photons or coherent light pulses, are used to implement quantum walks. The coherence properties allow for the maintenance of quantum superposition and interference effects that distinguish quantum walks from classical random walks.
53. What is the significance of coherence in optical parametric oscillators (OPOs)?
In OPOs, the coherence of the pump laser is transferred to the generated signal and idler beams through the nonlinear optical process. The coherence properties of the input determine the spectral and temporal characteristics of the output beams.
54. How does coherence affect the operation of a Sagnac interferometer?
The coherence of the light source in a Sagnac interferometer determines its sensitivity to rotation. Higher coherence allows for the detection of smaller phase shifts, enabling more precise measurements of angular velocity in applications like fiber optic gyroscopes.
55. What is coherent control in quantum optics?
Coherent control refers to the manipulation of quantum systems using coherent light fields. It involves using the phase and amplitude of light to steer quantum processes, such as selective excitation of molecular states or control of chemical reactions.
56. How do coherent sources enable the creation of optical atomic clocks?
Coherent sources, particularly ultra-stable lasers, are essential for optical atomic clocks. They provide the precise frequency reference needed to probe atomic transitions, allowing for extremely accurate time-keeping and frequency standards.

Articles

Back to top