Electromagnetic waves are disturbances that transfer energy through electric and magnetic fields and propagate through space and other mediums without requiring a medium. They are composed of oscillating electric and magnetic fields that interact with and transfer energy to matter. Electromagnetic waves include visible light and have a wide range of wavelengths, travel at the speed of light, and are the primary means by which energy is transferred between the Earth and the rest of the universe.

1. Electromagnetic waves

2. • Wave : a disturbance that transfers energy. Carry energy from one place to
another.
• But Electromagnetic waves are disturbances that transfers energy through a field.
• Energy that moves in the form of EM waves is called radiation.
• Electromagnetic (EM) waves propagate through space and can propagate through
any medium.
• They are a natural phenomenon
• Virtually all energy exchange between the Earth and the rest of the Universe is by
EM radiation.
• EM waves is a set of two transverse waves that move perpendicular to each other.
(Electric and magnetic field). Transverse waves do NOT require a medium to travel.
• They are composed of changing electric and magnetic fields.
• Electromagnetic waves interact with matter. Some substance absorb EM waves,
some reflect and others transmit.
• EM waves has no mass , but carry energy and momentum.
• Predicted : James Maxwell in 1870.
• Proved : Hertz in 1888.

3. • Sun is the main source of EM waves and provides most of the energy for Earth.
• Stars also give out EM waves but mostly they don’t reach earth because of the
distance between the stars and earth.
• EM waves do not lose energy as they move so they can move for ever.
• They travel at constant speed, 300,000 km/sec in space.
• Sun rays take 8 min to reach Earth
• Light is a form of EM radiation (Maxwell)
• Created by vibrating electric charges.
• When electric charg vibrates, the electric field around it changes creating magnetic
field. The magnetic and electric field create each other again.

10. Imagine that the vector field F pictured below gives the velocity of some fluid flow.
It appears that the fluid is exploding
outward from the origin. This
expansion of fluid flowing with velocity
field F is captured by the divergence of
F, which we denote divF. The
divergence of the above vector field is
positive since the flow is expanding.
In above, vector field represents
fluid flowing so that it compresses
as it moves toward the origin.
Since this compression of fluid is
the opposite of expansion, the
divergence of this vector field is
negative.

11. A path-dependent vector field with zero curl

12. Electric Displacement Vector : Electric Displacement vector denoted by D, accounts
for the effects of free and bound charges within materials. This appears in
Maxwells Equation.
Watch video on understanding Maxwells Equation
https://www.youtube.com/watch?v=FSEJ4YLXtt8&t=222s

13. If the electric charge distribution is known, then
the electric field produced can be calculated.
•The divergence of the magnetic field at any point
is zero.
•The assumption that there are no magnetic
monopoles.
A circulating electric field is produced by a
magnetic field that changes with time.
A circulating magnetic field is produced by an electric
current and or by an electric field that changes with time.

17. Ampere-Maxwell's Law

19. Properties
The properties of displacement current are mentioned below,
•It is a vector quantity and obeys the property of continuity in a closed path.
•It changes with the rate of change of current in an electric density field.
•It gives zero magnitudes when the current in an electric field of a wire is steady
•It depends on the varying time of an electric field.
•It had both direction and magnitude, which can be a value of positive, negative, or zero
•The length of this can be taken as the minimum distance from the starting point to the
ending point regardless of the path.
•It can be measured in a unit of length
•It has a minimum or maximum or equal magnitude of displacement for a given time to
the actual distance from the point.
•It depends on an electromagnetic field.
•It gives zero value when the starting point and the ending point is the same