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A brief note on Coherent and Incoherent Sources

Coherence light indicates the zero phase difference light and has the same frequency whereas incoherent light indicates different phase and random frequencies of light waves.

Coherent light and incoherent light are the parts of light sources that have different wave identification while traversing from one medium to another medium. These two light sources have different light patterns and emissions. Coherent light sources refer to the source of lights that have a constant phase difference. The nature of coherence light is the same as monochromatic light. Monochromatic light indicates the same and constant frequency light, as well as coherent light, refers to those lights that have the same frequency and same phase. There are various contrasts between coherent and incoherent light sources for their difference in phase in a certain situation.

Overview of Coherent Light and Incoherent Light 

Coherent light sources are the waves of light that belong in constant phase difference and same light frequency. A coherent light can be defined as monochromatic light if the light waves follow the same frequency while transferring from one medium to another medium. The monochromatic light has the same wavelength and same amplitude. Due to this reason, the waves belong in constant phase differences and have the same frequencies. Two waves can be said as coherent light if the light waves are independent of time. The waveform of lights is the same and amplitude is preferably equal to each other. The Sun is the best example of coherent sources that impact speckles for making images in a microscope plane.

Incoherent light identifies the lights which have different phases and changeable frequencies based on time. In that case, incoherent light depends on the time. Whenever there is a change in the movement of time, the phase of incoherent light also randomly changes. These light sources have no photon ion with constant phase difference and do not have a wavelength. The coherent lights are diffused in nature as if a light torch flashes on a dark area or basement then it diffuses and does not come into steady form. Electromagnetism is an example of incoherent light where the lights have been visualised from a certain point. Furthermore, night lamps and electric bulbs are real-life examples of incoherent sources of light. 

Difference between the Phenomenon of Coherent and Incoherent Light

Coherent light sources are the light sources that have constant phase differences and as well as same frequencies. Coherent light consists of one frequency and one wavelength. Incoherent light has different light frequencies and has a randomly changeable frequency. Coherent light sources always do not depend on the time whereas coherent light depends on types. A coherent light can be defined as monochromatic light but incoherent light cannot be said to be monochromatic light as multiple waves are involved in the incoherent light. Another difference that can be seen in this context is that Coherent light can be seen in one colour but incoherent light is the combination of multiple coherent lights. 

Source of Coherent and Incoherent Light

The Source of coherent light means the source of light which releases or emits light at the same frequency and wavelength. A coherent source can be produced by the superposition of light waves where the interference pattern of light will be maximum or minimum. At constant phase difference, a coherent source can be constructed in a light slit. Sunlight and laser lights are evidence of coherent light. Incoherent light sources define light that has different wavelengths, frequencies and different phases. The energy level of light continuously changes and also changes the phase of sources.


Conclusively, Incoherent and coherent lights are important components that are related to monochromatic light. This is regarded as one of the essential chapters in the subject of physics that need to be knowledgeable by all the learners of this subject. The overview of these two lights is given in the first place which gives a basic idea about its concept. The differences between these two lights are also analysed here to show the individuality of each light. The sources of incoherent and coherent light waves are also demonstrated in this process to give a higher knowledge about its usage in real life.


Frequently asked questions

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What is a coherent light source?

Ans.The coherent light sources are the light that has constant frequency and belongs in constant phase differences. A coherent light can be said to...Read full

What is an incoherent light source?

Ans. An incoherent light source refers to light that has different phase differences and frequencies. Incoherent lig...Read full

What are examples of coherent light sources and incoherent light sources?

Ans. Sound waves and laser light are examples of coherent light sources. In physics, a young slit can help to produc...Read full

Why are most lights regarded as coherent?

Ans. Most of the light pattern has been made into incoherent light sources to define bright and dark fringes in the ...Read full