Physics

Electromagnetic Waves

Defination of Wave

Wave is the way of transport of energy without the transport of matter. In other words, a wave can be described as a disturbance that travels through a medium, transporting energy from its source to another location without transporting matter. 

Types of Waves

Mainly there are two types of waves to transport energy from a location to another location.

1) Mechanical Waves

Mechanical waves are caused by a disturbance in the matter, whether solid, gas, liquid, or plasma. The matter that waves are traveling through is called a medium. Waves in water and sound waves in the air are two examples of mechanical waves.

MECHANICAL WAVES
Ocean waves – the medium through which they travel is water. Guitar and cello strings – the medium through which they travel is air.

2) Electromagnetic Waves

In the 1870’s, a Scottish scientist named James Clerk Maxwell told that when an electric field comes in contact with a magnetic field Electromagnetic waves are formed. The electric field and magnetic field of an electromagnetic wave are perpendicular to each other. Thus two fields become sources of each other and the wave propagates in a direction perpendicular to both the fields. These waves travel with a constant velocity of 3.00 x 108 ms-1 in a vacuum. Electromagnetic waves do not require a medium to propagate. This means that electromagnetic waves can travel in the vacuum of space also.

ELECTROMAGNETIC WAVES

Electromagnetic radiation

Electromagnetic radiation is caused to electromagnetic waves, propagating through space, carrying electromagnetic radiant energy.  Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays are examples of Electromagnetic radiation. All of these waves form part of the electromagnetic spectrum. Electromagnetic waves are created due to periodic changes of the electric or magnetic fields. The position of a specific electromagnetic wave within the electromagnetic spectrum can be known by either its frequency of oscillation or its wavelength. The entire electromagnetic spectrum, from the lowest to the highest frequency includes all radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. All frequencies and wavelengths of electromagnetic radiation can be used for spectroscopy.

Electromagnetic spectrum
Semi-circular meter diagram of the electromagnetic spectrum, from the low frequency (long wavelength) end of the spectrum, radio waves, microwaves, infrared, to the visible light, to the high-frequency (short wavelength) end, ultraviolet, X-rays, and gamma rays.

Frequency and Wavelength range of Electromagnetic Waves

Type of Radiation Frequency Range (Hz) Wavelength Range
Gamma-rays 1020 – 1024 < 10-12 m
X-rays 1017 – 1020 1 nm – 1 pm
Ultraviolet 1015 – 1017 400 nm – 1 nm
Visible 4 – 7.5*1014 750 nm – 400 nm
Near-infrared 1*1014 – 4*1014 2.5 μm – 750 nm
Infrared 1013 – 1014 25 μm – 2.5 μm
Microwaves 3*1011 – 1013 1 mm – 25 μm
Radio waves < 3*1011 > 1 mm

Electromagnetic waves are emitted by electrically charged particles undergoing acceleration and these waves can subsequently interact with other charged particles, exerting force on them.        

Dual Personality of Electromagnetic Waves:

ELECTROMAGNETIC WAVES

Scientists have observed that electromagnetic radiation has a dual “personality.” Besides acting like waves, it acts like a stream of particles (called “photons”) that have no mass. The photons with the highest energy correspond to the shortest wavelengths.

Uses of Electromagnetic Waves

Ultraviolet: Energy-efficient lamps, sun tanning, sterilization, vitamin D production Ozone depletion, etc.

Radio waves: Radio and television, accelerating charges, Remote controls, etc. 
Microwaves: Satellite communications and thermal agitation, Ovens, Radar, Cell phone, etc.
Infrared: Electrical heaters, cooking food, electronic transitions, and infrared cameras, etc.
X-rays: Medical imaging and treatments, Inner electronic transitions and fast collisions security, etc.
Gamma rays: Medical imaging and treatments, nuclear medicine, security, etc.
Visible light: Fiber optic communications, thermal agitation and electronic transitions photosynthesis, human vision, etc.

USES OF ELECTROMAGNETIC WAVES

In general, the applications of EM waves significantly depend on their corresponding frequency. Harnessing the capabilities of EM waves has led to great impacts on various fields such as wireless communication, industrial sensing/imaging, biomedical imaging and treatment, remote sensing, radar, security screening, etc.

Important Questions

Question 1: How are electromagnetic waves generated?

Answer: When an electric field comes in contact with a magnetic field Electromagnetic waves are formed. Electromagnetic waves are created due to periodic changes of the electric or magnetic fields.  

Question 2: How are electromagnetic waves propagated?

Answer: Electromagnetic waves do not require a medium to propagate. This means that electromagnetic waves can travel in the vacuum of space also.

Question 3: What is the velocity of electromagnetic waves?

Answer: Electromagnetic waves travel with a constant velocity of 3.00 x 108 ms-1 in a vacuum. 

Question 4: How is known the position of a specific electromagnetic wave?

Answer: The position of a specific electromagnetic wave within the electromagnetic spectrum can be known by either its frequency of oscillation or its wavelength.

Question 5: What is the way of transport of energy without the transport of matter?

Answer: Wave is the way of transport of energy without the transport of matter. In other words, a wave can be described as a disturbance that travels through a medium, transporting energy from its source to another location without transporting matter. 

Question 6: What are the main types of waves to transport energy from a location to another location?   

Answer: Mainly there are two types of waves to transport energy from a location to another location.

(a) Mechanical waves

(b) Electromagnetic waves

Question 7: What are mechanical waves?

Answer: Mechanical waves are caused by a disturbance in the matter, whether solid, gas, liquid, or plasma. The matter that waves are traveling through is called a medium. Waves in water and sound waves in the air are two examples of mechanical waves.

Question 8: What if electromagnetic radiation?

Answer: Electromagnetic radiation is caused to electromagnetic waves, propagating through space, carrying electromagnetic radiant energy. Electromagnetic waves are created due to periodic changes of the electric or magnetic fields. Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays are examples of Electromagnetic radiation.

Question 9: What is the dual personality of electromagnetic waves?

Answer: Scientists have observed that electromagnetic radiation has a dual “personality.” Besides acting like waves, it acts like a stream of particles (called “photons”) that have no mass. The photons with the highest energy correspond to the shortest wavelengths.

Question 10: What are the major applications of electromagnetic waves (EM)?

Answer: EM waves have led to great impacts on various fields such as wireless communication, industrial sensing/imaging, biomedical imaging and treatment, remote sensing, radar, security screening, etc.

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