**Electromagnetic waves Physics Theory**is a special gift of nature. So You are going to learn here the best concept of

**Electromagnetic Waves**in simple and with Easy Examples.

**Electromagnetic waves**?.

**electromagnetic waves**is created ? As well as Types of electromagnetic waves . And Application and uses of electromagnetic waves.

## Electromagnetic waves is a special gift of nature

This world work on nature principle, Today you are able to talk 1000 km far distance with other peoples sitting in other countries,

Electromagnetic wave |

**f = c/**𝛌

**f = c/**𝛌 f = 3×10⁸/500×10⁻⁹ = 6×10¹⁴ HZ for visible light 𝛌 = 500nm.

**f = c/**𝛌 = 3×10⁸/9.35×10⁻⁶ = 3.2×10¹³ HZ.

## What is electromagnetic waves ?

First you should understand what is wave ? then i will explain electromagnetic wave,

Electromagnetic Wave |

### Electromagnetic waves theory history

It is very important to know the electromagnetic wave theory,

Displacement Current |

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**Important conclusion**

**WRONG.**it must give the same value but not like this.

**Ampere’s Maxwell Law**

∫B.dl = 𝞵₀iₑₙ + 𝞵₀𝝐₀d𝛟ₑ/dt = 𝞵₀(iₑₙ + 𝝐₀d𝛟ₑ/dt) , Now see the dimension of 𝝐₀d𝛟ₑ/dt is current dimension. well iₑₙ is called conduction current and 𝝐₀d𝛟ₑ/dt is called displacement current this name was given by Maxwell.

Now see the sixth case of circuit carefully, where capacitor plate having charge (+Q) and (-Q), As the current will flow through circuit the value of charge at capacitor (+Q) will increase, and due to this charge there will be a electric field between capacitor as shown and i have stated this earlier.

Now the term 𝝐₀d𝛟ₑ/dt is associated with electric field, because d𝛟ₑ/dt is electric flux, see the term 𝝐₀d𝛟ₑ/dt is displacement current name given by Maxwell but actually this is not current, This is simply associated with electric field as shown in sixth case, whereas Maxwell given this name as current, because its dimension is same as current.

Now you can write the above expression 𝞵₀(iₑₙ + 𝝐₀d𝛟ₑ/dt) = 𝞵₀(ic +id) where ic is conduction current i which is flowing in the circuit as shown.id is displacement current

id current is in between the capacitor as told by Maxwell.

Now **important concept **conduction current is due to flow of charge, but when Maxwell is saying displacement current is in between the capacitors then there is flow of charge between the capacitor plate, Is it correct ? BIG no.

It is clear that there is no any charge flow between the two capacitor plate. So you must understand that displacement current does not mean flow of charge. Then what is meaning of displacement current here ?.

Well displacement current meaning here is changing in electric field. But how ? see as the current will flow through the circuit, then charge (+Q) will accumulate at capacitor plate so charge (+Q) will increase and hence electric field will increase.

So it is very simple displacement current is due to changing electric field, you can see the mathematical expression for displacement current id = 𝝐₀d𝛟ₑ/dt , where d𝛟ₑ/dt is electric flux .

### BIG Important Concept for displacement current

Due to changing electric field produce displacement current, Now you think electric field is a vector quantity, Hence electric field can change by two ways first either by changing its magnitude or second way by changing its direction only keeping magnitude constant, So here this is case of due to changing both magnitude as well as direction of electric field hence electric field are changing here due to both magnitude as well as direction, so finally changing electric flux.

For second case keep charge magnitude constant and accelerate that charge back and forth in this case electric field direction will change, so this is also changing electric field hence displacement current will also be there without flow of charge.

Now third case take a stationary charge will it change electric field ? No because neither electric field direction changing nor its magnitude is changing.

Hence a stationary charge will not change electric field, so no displacement current will be due to stationary charge.

Mathematically you can see if electric field is constant then electric flux will be also constant and hence d𝛟ₑ/dt will be zero, Hence displacement current will be zero.

### Conduction and displacement current create magnetic field

Conduction and displacement current |

From the first figure conduction current ic carries charge so at positive plate Q will accumulate and value of Q will go on increasing, Hence electric field will also increase as shown in figure. Hence changing electric field so create displacement current as shown.

### How does electromagnetic wave is created ?

Source of electromagnetic wave is accelerating charge, Due to this accelerating charge electric field is changes and due to electric field changes magnetic field is created, Hence due to electric and magnetic field changes electromagnetic wave is created.

**Now you must understand charge properties in different states.**

### Properties of electromagnetic waves

### Electromagnetic waves equation

See below wave equation varying with time magnitude of electric field as well as magnetic field change,according to displacement and time.

You should remember that electric field and magnetic field are always perpendicular to each other and wave propagation equation also perpendicular to both electric and magnetic field

Wave Equation |

where 𝛚 is angular frequency, k = 2𝛑/𝛌 is called wave constant or wave number .

E₍ₓ,ₜ₎ = Eₘcos(kx-𝛚t +𝛟) , B₍z,ₜ₎ = Bₘcos(kx-𝛚t +𝛟) , This is the equation of electric and magnetic field.

questions are asked on the basis of this equation, compare and find the required parameter 𝛌 , 𝛚 , 𝛋 and 𝛎 , 𝛟 So remember the equation to find the asked value above relations.

### Electromagnetic waves source

The source of electromagnetic wave is electric charge, You know there are two basic characteristics of material one is mass and other is electric charge. Mass is that characteristics, which creates gravitational field. you can refer **gravitational field concepts**.

Charge is that characteristics, which creates electric field around it. there can be three state of a charge.

1 A stationary charge ( Velocity is zero )

2 A moving charge ( Velocity is constant )

3 An accelerating charge ( Velocity is variable )

According to this velocity there is effect around it. A stationary charge create stationary electric field. And a moving charge create electric field as well as magnetic field.

Sample of moving charge is current in a conductor see below picture.

Electromagnetic wave source |

Conductor carrying current is not charge body because every time number of proton and number of electron in conductor is same, so it is not a charge body.So it can’t create electric field.

see at one end electron inter in conductor and same time other end electron out from conductor hence net charge on conductor is always zero, electron in motion but number of electron and proton are always same on conductor body.

So current in a conductor only create magnetic field. Hence current in a conductor does not create electromagnetic wave.

Accelerating charge as shown in figure q create electric field, due to motion of charge create magnetic field and due to increase in charge velocity both electric and magnetic field are pushed forward.

So electric and magnetic field start moving forward. Hence accelerating charge create electromagnetic wave.

#### Electromagnetic waves propagation

**electromagnetic wave.**I want your feedback, comments, like and share, learn more and grow thanks for sharing.

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