Electromagnetic Radiation Meaning
EMR Meaning: In physics, electromagnetic radiation (EM radiation or EMR) alludes to the waves (or their quanta, photons) of the electromagnetic field, spreading (emanating) through space, conveying electromagnetic radiant energy.
Electromagnetic Behaviour:
Electromagnetic waves are radiated by electrically charged particles going through acceleration, and these waves can consequently interact with other charged particles, applying force on them.
Electromagnetic Properties:
EM waves convey energy, momentum, and angular momentum (precise energy) away from their source particle and can grant those quantities to matter with which they interact.
On this page, we will discuss the properties and behaviour of EMR in detail.
Electromagnetic Radiation
Electromagnetic Radiation incorporates radio waves, microwaves, infrared, (visible) light, bright, X-rays, and gamma rays. These waves structure part of the electromagnetic spectrum/range.
Now, let’s understand the science behind the electromagnetic range:
Classically, electromagnetic radiation comprises electromagnetic waves, which are synchronized oscillations/vibrations of electric and magnetic fields.
In a vacuum, electromagnetic waves travel at the speed of light, generally meant c. In a homogeneous, isotropic media, the motions of the two fields are perpendicular to one another and to the direction of energy and wave proliferation, framing a transverse/crossover wave.
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The wavefront of electromagnetic waves transmitted from a point source (like a light) is a sphere.
The position of an electromagnetic wave inside the electromagnetic range can be portrayed by either its frequency of wavering/oscillations or its frequency. The electromagnetic spectrum of various frequencies is called by various names since they have various sources and impacts on the matter. Arranged by increasing frequency and decreasing wavelength, and vice-versa, these are radio waves, microwaves, infrared radiation, visible light, bright radiation, X-rays, and gamma rays.
Electromagnetic Radiation - Properties and Behaviour
In regular human experience, the impression of visible light, followed by radio waves, infrared radiation, and bright beams, are the most pertinent and ever now and again experienced bits of the electromagnetic range. The impression of higher energy X-rays, for example, gets pertinent for X-ray space telescopes and atomic weapons examination and plan. This page will manage the regular types of electromagnetic radiation with its properties and behaviour.
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Scattering Reflection and Refraction
The below image shows the scattering, reflection, and refraction of electromagnetic radiation:
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Scattering:
All electromagnetic radiation is liable to scattering/dispersing by the medium, viz: gas, fluid, or solid) through which it passes.
The cycle where energy is taken out from a beam of electromagnetic radiation and reemitted with an adjustment in a direction, phase, or wavelength is known as the scattering of Electromagnetic radiation.
The scattering process in these wavelength regions comprises of speed increase of the electrons (acceleration of a charge) by the incident beam, trailed by reradiation from the speeding up charges. It is divided into the following types:
Scattering processes might be partitioned by the time between the absorption of energy from the incident beam, and the resulting reradiation. These are as follows:
Inelastic scattering
Brillouin and Rayleigh scattering
Large particles (Tyndall Effect)
Critical opalescence (Coherent Electromagnetic Waves)
Nonlinear scattering
Do You Know?
It has been known since crafted by J. Maxwell in the nineteenth century that speeding up electric charges emanate energy and, on the other hand, that electromagnetic radiation comprises fields that speed up charged particles.
Light in the visible, infrared, or ultraviolet region interacts essentially with the electrons in gases, fluids, and solids but not the nuclei.
Reflection
The returning or tossing back of electromagnetic radiation by a surface whereupon the radiation is occurrence. All in all, a reflecting surface is a limit between two materials of various electromagnetic properties, like the limit among air and glass, air and water, or air and metal.
Key Concepts:
The impression of electromagnetic radiation includes the returning or tossing back of the radiation by a surface whereupon the radiation is occurrence.
A reflecting surface is by and large the limit between two materials of various electromagnetic properties.
Devices designed/intended to reflect radiation (EMR) are called reflectors or mirrors.
The reflectivity of a surface is a proportion of the measure of reflected radiation.
Antireflection coatings are utilized to diminish the reflection from surfaces of optical hardware and devices.
Refraction
The change of course/direction of propagation of any wave marvel happens when the wave speed changes. The term is most regularly applied to visible light, yet it likewise applies to any remaining electromagnetic waves, just as to sound and water waves.
Coherent Electromagnetic Waves
As we know that light sources produce light waves of varying frequencies. For instance, an incandescent lamp covers a low transmission range (high-frequency), while a laser produces a low-range frequency.
So, the source that produces a single and a narrow frequency is the coherent source and the property is the coherence.
The different light sources from coherent light sources interfere with each other and get combined in a space to sum and differentiate electromagnetic waves.
So, the coherence of electromagnetic waves is an ability to interfere/combine to produce interference patterns. We also call this a degree of coherence.
Fun Fact
Magnetism and Electricity were once considered discrete forces. Nonetheless, in the year 1873, Clerk Maxwell, a Scottish physicist built up a Unified Theory of electromagnetism.
FAQs on Properties and Behavior of Electromagnetic Radiation
1. What are the fundamental properties of electromagnetic (EM) waves as per the CBSE Class 12 syllabus?
Electromagnetic waves have several key properties that define their nature and behavior. According to the CBSE syllabus for the 2025-26 session, the main properties are:
- Source: They are produced by accelerating charged particles.
- Nature of Wave: They are transverse waves, meaning the oscillations of the electric and magnetic fields are perpendicular to the direction of wave propagation.
- Propagation: They do not require any material medium for propagation and can travel through a vacuum.
- Speed: In a vacuum, all electromagnetic waves travel at the same constant speed, the speed of light (c ≈ 3 x 10⁸ m/s).
- Energy and Momentum: They carry energy and momentum, which they can transfer to matter upon interaction.
- Field Relationship: The electric (E) and magnetic (B) fields oscillate in the same phase and are perpendicular to each other.
2. What is the electromagnetic spectrum, and how are its different regions classified?
The electromagnetic spectrum is the complete range of all types of electromagnetic radiation, arranged in order of increasing frequency (and decreasing wavelength). The main regions, from lowest to highest frequency, are:
- Radio waves: Used in radio and television communication systems.
- Microwaves: Used in radar systems for aircraft navigation and in microwave ovens for cooking.
- Infrared waves: Emitted by hot bodies, used in thermal imaging, remote controls, and physical therapy.
- Visible light: The only part of the spectrum visible to the human eye, responsible for our sense of sight.
- Ultraviolet (UV) rays: A component of solar radiation, used for sterilising medical equipment and in water purifiers.
- X-rays: Used in medical diagnostics to image bones and in engineering to detect cracks in structures.
- Gamma rays: The most energetic waves, produced in nuclear reactions and used in radiotherapy to treat cancer.
3. How does electromagnetic radiation typically behave when it encounters a medium?
When electromagnetic radiation, such as light, travels from one medium to another, it can exhibit several behaviors, primarily:
- Reflection: The wave bounces off the surface of the new medium. A common example is light reflecting off a mirror.
- Refraction: The wave bends as it passes through the surface into the new medium. This happens because the speed of the wave changes, for instance, when light enters water from air.
- Absorption: The energy of the wave is absorbed by the particles of the medium, often converting into thermal energy. This is why dark-colored objects get warm in the sun.
- Scattering: The wave is redirected in multiple directions by particles in the medium. The blue color of the sky is a classic example of the scattering of sunlight by air molecules.
4. Why are electromagnetic waves considered transverse waves?
Electromagnetic waves are classified as transverse waves because the directions of their oscillating components are perpendicular to the direction of their travel. In an EM wave, both the electric field (E) and the magnetic field (B) oscillate. Crucially, these oscillations are at a right angle (90°) to each other and, at the same time, both are at a right angle to the direction in which the wave is propagating. This is fundamentally different from longitudinal waves (like sound), where the oscillations are parallel to the direction of wave travel.
5. How is electromagnetic radiation produced, and what factor determines its type (e.g., radio wave vs. X-ray)?
Electromagnetic radiation is fundamentally produced whenever an electric charge undergoes acceleration. A stationary charge creates only an electric field, and a charge moving at a constant velocity creates both electric and magnetic fields, but it takes an accelerating charge to create the propagating disturbance that we call an electromagnetic wave. The frequency of the charge's oscillation or acceleration is the key factor that determines the type of EM radiation produced. For example, low-frequency oscillations in an antenna produce radio waves, while the rapid deceleration of high-energy electrons in a metal target produces high-frequency X-rays.
6. What is the importance of coherence in the context of electromagnetic waves?
Coherence is a property of waves that describes the constancy of the phase relationship between them. For electromagnetic waves, coherence is important because it is a necessary condition for waves to produce a stable and observable interference pattern. A coherent source, like a laser, emits light waves that are in phase with each other, allowing them to interfere constructively (to create brighter spots) and destructively (to create darker spots) in a predictable way. In contrast, an incoherent source, like a standard light bulb, emits waves with random phases, so any interference effects are fleeting and average out, preventing a clear pattern from forming.
7. Besides visible light, what are some real-world examples of how different EM waves are used in technology?
Beyond visible light, our modern world relies heavily on various forms of electromagnetic radiation. Here are some key examples:
- Wi-Fi and Bluetooth: These technologies use radio waves and microwaves to transmit data wirelessly between devices.
- TV Remote Controls: Most remotes use beams of infrared (IR) radiation to send signals to the television.
- Medical Sterilisation: Hospitals use ultraviolet (UV) radiation to kill bacteria and viruses on equipment, a process known as UV germicidal irradiation.
- Airport Security: Baggage scanners use X-rays to see inside luggage and check for prohibited items without having to open them.
