# What is Coherence in physics ?

Do you searching about what is coherence ? According to physics definition of coherence  When two or more electromagnetic waves are said to be coherent, their frequency is the same and they are in phase or maintain a steady phase difference with them. In general, the phase may vary from one point to another or may change from time to time.To generate interference, coherent light sources are required. The concept of coherence is explained below.

 coherence physics

## Types of  Coherence

We have two distinct coherence, namely (i) temporal coherence and (ii) spatial coherence.

### (i) Temporal coherence This refers to the correlation between the field of a wave at one point at some point and the field at the same point at a later time.Temporal coherence is refers only a single beam of light

(ii) spatial coherence If there is a constant phase difference in the space between the waves at different points for a time t, they are called spatial coherent.It refers  the relationship between two separate beams of light.

## what are example of coherence ?

1. Laser light -  Laser light is an example of a coherent light source. The light emitted by the laser light has the same frequency and phase.

2. Sound waves - Sound wave are another example of coherent sources. The electrical signals of the sound waves travel with the same frequency and phase.

## Interference in thin films by reflection

When white light (sunlight) falls on thin films such as soap bubbles or air films, beautiful colors will appear due to interference. The interference of light in thin films can be explained by allowing monochromatic illumination of wave length λ ′, which can fall on a thin film of thickness ′ t, as shown in the given figure. Let the refractive index of film material be material μ .

AB is a monochromatic incident light beam at "B" in an equally thick transparent film. A portion of the beam is reflected along BC and the remaining light is refracted with BD. A portion of the refracted ray is reflected with D in "D". Then, this beam refracts with EF at "E" and enters the air. Re BC and EF are parallel and overlap to produce interference. The intensity of the interference fringe depends on the path difference between BC and EF rays. The path difference "path" is given below

 Interference in thin films by reflection

### Biasing of p–n Junction | Forward and Reverse-biased |

Biasing the p-n junction means applying some external voltage to both sides of the p-n junction. Reverse-biased junction and forward-biased junction are two types of biased junction. You should have also good understanding of  N-Type and P-Type Semiconductor before moving towards this topic.

Biasing of p–n Junction Biasing of a p–n junction means uses of some external voltage across the two sides of the p–n junction. It is divided into two groups
Forward-biased junction : When the p-side of junction  is connected to the positive terminal of a battery and the n-side of junction is connected to the negative terminal, the p–n junction is said to be a forward-biased junction. Reverse-biased junction :If the positive terminal of the battery is connected to the n-side of junction and the negative terminal on the p-side, the p–n junction is said to be a reverse-biased junction.Now we will see about forward and reverse-biased junction in detail.
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If you are search about how to study science so i am going to share with you some tips that help you to study science in effective way. In this post, we are going to see what you should keep in mind while studying science. Because of which you can complete the syllabus of your science subject in the least time and comfortably and can  study  well with full concentration. So I will tell you five such tips with which you can study science comfortably.

How to study scienceWhether you are a student of class 10, whether in class 12 or any class, while studying science, these five tips will help you to get good score in science as well as improving your interests in science .

Goal Setting : By Goal Setting, I mean that when you sit for study, you have to set this target that today I will read so much chapter or today I will get up after reading so much content.This thing will do the work of positive motivation and will push you that we have to study till then. Until my target is achieved.
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We see applications of electricity all around us.Today we will discuss about the need to study electrical  engineering .We observe the presence of electricity around us. This is really amazing and it is also interesting to know how mankind can power its use. All electronic and electrical products operate on electricity.  Be it your computer system, cell phone, home entertainment system, lighting, heating and air conditioning system - all are examples of electrical applications. The application of electricity is infinite and often extends beyond our imagination.

The need to study electrical engineering We have need to study electrical engineering because of following reason .Which is discussed below in given points.
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