Name: electromagnetic waves in everyday technology
Uploaded: 2025-05-22T09:05:53.000Z
Duration: 1 min 24 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Physical Science

Waves and Electromagnetic Radiation

3.2.9-12.V

The Electromagnetic Spectrum

Lo spettro elettromagnetico è la distribuzione delle onde elettromagnetiche in base alla loro lunghezza d'onda o frequenza. Include onde radio, microonde, radiazioni infrarosse, luce visibile, raggi ultravioletti, raggi X e raggi gamma.
Le onde radio hanno la lunghezza d'onda più lunga dello spettro, che va da millimetri a chilometri. Sono generati da cariche elettriche accelerate e fungono da vettore per trasmettere informazioni.
Un forno a microonde produce microonde che riscaldano il cibo.
Le superfici riscaldate emettono radiazioni infrarosse. I telecomandi utilizzano radiazioni infrarosse di lunghezza d'onda di circa 0,9 micrometri.
Una lampadina a incandescenza emette radiazioni visibili con lunghezze d'onda che vanno da 0,4 a 0,7 micrometri.
I raggi ultravioletti di lunghezza d'onda di circa 0,35 micrometri vengono utilizzati per uccidere gli insetti.
Le sorgenti di raggi X ad alta frequenza sono transizioni intraatomiche. I raggi X con lunghezza d'onda di circa 1 x 10-4 micrometri vengono utilizzati per la scansione delle ossa.
I raggi gamma vengono emessi durante il decadimento nucleare. La radioterapia utilizza i raggi gamma.

<ol>
	<li>OpenStax. (2019). Fisica universitaria Vol. 2. [Versione web]. Estratto da <a href="https://openstax.org/books/university-physics-volume-2@8ede2ba/pages/16-5-the-electromagnetic-spectrum">https://openstax.org/books/university-physics-volume-2@8ede2ba/pages/16-5-the-electromagnetic-spectrum</a></li>
</ol>

lo spettro elettromagnetico

Le onde elettromagnetiche sono categorizzate in base alle loro lunghezze d'onda e frequenze, dando origine allo spettro elettromagnetico. Queste onde sono classificate come radio, infrarosso, ultravioletto, eccetera. Le onde radio si riferiscono alla radiazione elettromagnetica con lunghezze d'onda che vanno da millimetri a chilometri. Le onde radio sono comunemente utilizzate per le comunicazioni audio (ad esempio, radio) e tipicamente derivano da una corrente alternata nei fili di un'antenna di trasmissione. Coprono un'ampia gamma di lunghezze d'onda e vengono utilizzate per la radio AM (modulata in ampiezza) e FM (modulata in frequenza), i telefoni cellulari e i segnali TV. Le microonde sono le onde elettromagnetiche ad alta frequenza, prodotte da correnti in circuiti e dispositivi macroscopici. Le frequenze delle microonde vanno da circa 109 Hz a quasi 1012 Hz. La maggior parte delle informazioni trasmesse dai satelliti viaggia attraverso le microonde. Il radar è una comune applicazione delle microonde. Rilevando e sincronizzando gli echi delle microonde, i sistemi radar possono determinare la distanza da oggetti diversi come nuvole, aeromobili o persino la superficie di Venere.

La radiazione infrarossa è generalmente prodotta dal moto termico e dalla vibrazione e rotazione degli atomi e delle molecole. Circa la metà dell'energia solare che arriva sulla Terra è nella regione infrarossa, con la maggior parte del resto nella parte visibile dello spettro. I satelliti di ricognizione possono rilevare edifici, veicoli e persino singoli esseri umani dalle loro emissioni infrarosse.

La luce visibile è il segmento stretto dello spettro elettromagnetico a cui risponde normalmente l'occhio umano. Solitamente ci riferiamo alla luce visibile come avente lunghezze d'onda comprese tra 400 nm e 750 nm. I raggi X sono prodotti dalle transizioni intra-atomiche e dalle collisioni veloci. Vengono utilizzati per immaginare oggetti opachi alla luce visibile, come il corpo umano o le parti degli aeromobili. I raggi gamma sono prodotti durante il decadimento nucleare e hanno la frequenza più alta dello spettro elettromagnetico.

Lo spettro elettromagnetico

Le onde elettromagnetiche sono classificate in base alle loro lunghezze d'onda e frequenze, fornendo lo spettro elettromagnetico. Queste onde sono classificate come ...

Education

Didattica

JoVE Core

Physics

Fisica

Unit 1

Unità 1

Electromagnetic Waves

Onde elettromagnetiche

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

electromagnetic waves in everyday technology

Electromagnetic waves are grouped by wavelength and frequency. This set of waves is called the electromagnetic spectrum. It includes radio waves, microwaves, infrared, visible light, X-rays, and gamma rays.

Radio waves have wavelengths from millimeters to kilometers. They are often used for audio communication, such as radios. In many cases, they come from alternating current in the wires of a broadcast antenna. Radio waves also carry AM and FM radio, cellular phone signals, and TV signals.

Microwaves are the highest-frequency electromagnetic waves. They are produced by currents in macroscopic circuits and devices. Their frequencies range from about 10^9 Hz to nearly 10^12 Hz. Most satellite-transmitted information is carried in microwaves, and radar is a common use. Radar measures the time of microwave echoes to find the distance to objects such as clouds, aircraft, or even the surface of Venus.

Infrared radiation is usually produced by thermal motion and by the vibration and rotation of atoms and molecules. About half of the solar energy that reaches Earth is in the infrared region. Most of the rest is in visible light. Infrared emissions can also be used by reconnaissance satellites to detect buildings, vehicles, and even individual humans.

Visible light is the narrow part of the spectrum that the normal human eye can detect. It has wavelengths between about 400 nm and 750 nm. X-rays come from intra-atomic transitions and fast collisions. They can image objects that are opaque to visible light, such as the human body or aircraft parts. Gamma rays are produced during nuclear decay and have the highest frequency in the electromagnetic spectrum.

Electromagnetic Waves in Everyday Technology

electromagnetic-waves-in-everyday-technology

electromagnetic waves

Maxwell’s Equations Behind EM Waves

Maxwell’s equations explain how electric and magnetic fields work together to create electromagnetic waves. James Clerk Maxwell brought together the ideas of Oersted, Coulomb, Gauss, and Faraday and built a single theory of electromagnetism. Together with the Lorentz force law, his equations describe the laws of electricity and magnetism. A key part of Maxwell’s work is the symmetry in the equations. Faraday’s law shows that a changing magnetic field produces an electric field. Maxwell added...

generating electromagnetic radiations

Hertz's Spark Gaps and Radio Waves

Heinrich Hertz used sparks and tuned circuits to show that electromagnetic waves could be produced in the lab. Starting in 1887, the German physicist ran experiments that confirmed electromagnetic waves exist and travel at the speed of light. Hertz built an alternating-current RLC circuit. RLC stands for resistor, inductor, and capacitor. The circuit was set to a known resonant frequency and connected to a loop of wire. High voltage across the gap in the loop created sparks. Those sparks gave...

the electromagnetic spectrum

Electromagnetic waves are grouped by wavelength and frequency. This set of waves is called the electromagnetic spectrum. It includes radio waves, microwaves, infrared, visible light, X-rays, and gamma rays. Radio waves have wavelengths from millimeters to kilometers. They are often used for audio communication, such as radios. In many cases, they come from alternating current in the wires of a broadcast antenna. Radio waves also carry AM and FM radio, cellular phone signals, and TV signals. <br...

electromagnetic wave equation

How Maxwell Linked Light to Waves

Maxwell's equations show how electric and magnetic fields behave in a vacuum, or empty space. They are written as differential equations and describe fields created by source charges, whether the charges are still or moving. These fields also act on a test charge, and its motion can be found with the right boundary conditions. The key question in empty space is what happens when there are no source charges. In the vacuum form of Maxwell's four equations, the first-order partial differential...

plane electromagnetic waves i

Transverse Fields in Electromagnetic Waves

Electromagnetic waves are made of electric and magnetic fields that move through space together. Maxwell's equations predict these waves, and they can travel in free space without a medium. The electric field acts on a stationary charge, while the magnetic field acts on a moving charge. For a wave traveling along the x-axis, the fields are written as Ey(x, t) and Bz(x, t). In free space, there are no free charges or currents, so the charge enclosed and current terms in Maxwell's equations are...

plane electromagnetic waves ii

Faraday’s Law in a Plane Wave

Faraday’s law can be used to link the electric and magnetic fields in a plane electromagnetic wave. Here, the wavefront moves in the x-direction at a constant speed. The goal is to show how the field strengths must be related for the wave to stay consistent with Faraday’s law. To apply the law, a rectangle of width a is placed with its area vector in the positive z-direction. The line integral is taken counterclockwise around the rectangle. One side lies outside the wavefront, so the electric...

propagation speed of electromagnetic waves

propagation-speed-of-electromagnetic-waves

Maxwell’s Equations and Light Speed

Electromagnetic waves follow Ampere’s law when there is no conduction current. A plane wavefront moves in the positive x-direction. To analyze it, a rectangle is placed in the xz-plane with its area vector pointing in the positive y-direction. The line integral around the rectangle is taken counterclockwise. The magnetic field is zero on some sides and perpendicular on others. It is parallel to one side, and that side gives a non-zero contribution to the integral. Because the left side of...

electromagnetic waves in matter

How Light Slows in Materials

Electromagnetic waves can travel through matter as well as through vacuum. Light is one example. It can move through air, water, or glass. When an electromagnetic wave passes through a dielectric medium, the equations that describe it change. In Ampere's law, the permittivity of free space, ε0, is replaced by the permittivity of the dielectric, ε. The vacuum permeability, μ0, is also replaced by the permeability of the medium, μ. The wave speed c in vacuum is then replaced by a lower speed, v,...

energy carried by electromagnetic waves

How EM Waves Transfer Energy

Electromagnetic waves transfer energy through their electric and magnetic fields. This energy can be easy to notice, like the warmth from the summer sun, or harder to feel, like the energy in gamma rays that can damage living cells. The fields in an electromagnetic wave can exert forces on charges in a system. They can move those charges and do work on them. Even if a wave is not absorbed right away, it still carries energy away from its source. If some of the wave energy is absorbed, the...

intensity of electromagnetic waves

Poynting Vector and Light Intensity

The Poynting vector describes the energy flux of an electromagnetic wave. It tells how much energy passes through a unit area in a unit time at a specific moment. For a plane electromagnetic wave moving along the x-axis, the energy flux depends on the peak electric field E0 and the peak magnetic field B0. For high-frequency waves, the energy flux changes very quickly with time. Visible light has a frequency on the order of 10^14 Hz, so its energy flux varies too fast to track directly. Most...

momentum and radiation pressure

Radiation Pressure in Light and Comets

Radiation pressure is the force that electromagnetic waves can exert on matter. It appears because light carries momentum, so an object that absorbs a wave feels a push in the direction the wave travels. This same force helps explain why sunlight can affect small particles in space. Maxwell predicted radiation pressure, and Nichols and Hull confirmed it in 1903. They used a torsion balance with mirrors suspended from a fiber inside a glass container. When they shone light on one mirror, the...

radiation pressure: problem solving

Radiation Pressure in Light and Space

Radiation pressure is the push that light can exert on matter. When an electromagnetic wave is completely absorbed by a surface, its energy density is transferred as momentum to that surface. The rate of momentum transfer on a surface perpendicular to the wave gives the force, and the force per unit area is the radiation pressure. A perfectly absorbing surface receives this pressure directly from the incoming wave. If the surface is perfectly reflecting, such as a metal surface, and the light...

standing electromagnetic waves

Electromagnetic Wave Reflection at Conductors

Electromagnetic waves can reflect from a conductor or a dielectric. When the reflected wave combines with the incoming wave, the result is a standing electromagnetic wave. This is similar to the standing waves formed on a stretched string. To see how this happens, consider a perfect conductor placed in the yz-plane. A linearly polarized electromagnetic wave moving in the negative x-direction strikes the surface. The electric field cannot have a component parallel to the surface of a perfect...

standing waves in a cavity

Electromagnetic Modes in a Microwave Cavity

Electromagnetic waves can form standing patterns inside a cavity. Household microwaves and lasers are common examples of this effect. When two conducting metal plates are placed parallel at the nodal planes, they create a space where standing waves can exist. The cavity between the plates works like a stretched string fixed at x = 0 and x = L. The distance L must be an integer multiple of half a wavelength. The wavelengths that meet this condition have matching frequencies, and each frequency,...

key terms and concepts

Explore how radio waves, microwaves, infrared, visible light, X-rays, and gamma rays are used in communication, imaging, radar, and detection.

Electromagnetic Waves in Everyday Technology | JoVE K12

physics

JoVE Core Physics introduces the theory and application of fundamental physics topics, including kinematics, dynamics, fluid mechanics, statics, waves, and acoustics, with concise and easy-to-understand animated videos. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

3.2.9-12.W

Louisiana Student Standards for Science

High School

Waves And Their Applications

HS-PS4-4

waves-and-their-applications-in-technologies-for-information-transfer

Waves And Their Applications In Technologies For Information Transfer

HS-PS4-1

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Energy And Waves

Waves

Light phenomena

Tennessee Academic Standards

Waves and Their Applications in Technologies for Information Transfer

PHYS.PS4.5

Virginia  Standards of Learning

HIgh School

PS.7

PS.7.b

PH.5

PH.5.c

PH.6

PH.6.a

PH.6.b

Minnesota Academic Standards in Science

3.2.2 9P.3.1.1.2

4.2.1 9P.3.2.2.1

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

HS-PS4-5

Arizona Science Standards

HS.P4

HS.P4U1.10

Alabama Course of Study Science

Earth and Space Science

Earth's Place in the Universe

9-12.ESS.1.2.b

9-12.ESS.1.2.c

9-12.ESS.1.3.a

9-12.P.3.7.c

Next Generation Science Standards

HS-PS4-2

HS-PS4-3

Earth’s Place in the Universe

HS-ESS1-1

Florida Department of Education

SC.912.P.10

SC.912.P.10.16

SC.912.P.10.17

SC.912.P.10.18

Texas Essential Knowledge and Skills

PHYS.8

PHYS.8.E

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

P-PS4-2

P-PS4-3

P-PS4-5

Earth and Space Science (ESS)

E-ESS1-1.

E-ESS1-2.

Earth’s Systems

E-ESS2-2.

E-ESS2-4.

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Waves and Electromagnetic Radiation

HS-PS4-4.

Earth and Space Sciences

Space Systems

HS-ESS1-1.

HS-ESS1-2.

Georgia Standards of Excellence

Astronomy

SAST2

SAST1.2

SP4.

mechanical-and-electromagnetic-waves-properties

Mechanical and Electromagnetic Waves Properties

Travelling Waves

A wave is a disturbance that propagates from its source, repeating itself periodically, and is typically associated with simple harmonic motion. ...

Wave Parameters

The simplest mechanical waves are associated with simple harmonic motion and repeat themselves for several cycles. These simple harmonic waves can be ...

Equations of Wave Motion

Mathematically, the motion of a wave can be studied using a wavefunction. Consider a string oscillating up and down in simple harmonic motion, having a ...

Graphing the Wave Function

Consider the wave equation for a sinusoidal wave moving in the positive x-direction. The wave equation is a function of both position and time. From the ...

/files/media/science-education/science-education-thumbs/14721.jpg

Velocity and Acceleration of a Wave

A wave propagates through a medium with a constant speed, known as a wave velocity. It is different from the speed of the particles of the medium, which ...

Speed of a Transverse Wave

The speed of a wave depends on the characteristics of the medium. For example, in the case of a guitar, the strings vibrate to produce the sound. The ...

/files/media/science-education/science-education-thumbs/14722.jpg

problem-solving-tuning-of-a-guitar-string

Problem-Solving: Tuning of a Guitar String

In the case of stringed instruments like the guitar, the elastic property that determines the speed of the sound produced is its linear mass density or ...

/files/media/science-education/science-education-thumbs/14744.jpg

Kinetic and Potential Energy of a Wave

All forms of waves carry energy; this is directly visualized in nature. For instance, the waves of earthquakes are so intense that they can shake huge ...

Energy and Power of a Wave

The total energy associated with a wavelength is the sum of the potential energy and the kinetic energy. The average rate of energy transfer associated ...

Students who demonstrate understanding can use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling in various media. Clarifying Statement: Examples of data could include electromagnetic radiation traveling in a vacuum and glass, sound waves traveling through air and water, and seismic waves traveling through the Earth. Assessment Boundry: Assessment is limited to algebraic relationships and describing those relationships qualitatively.

3.2.9-12.T

Interference and Superposition of Waves

When two waves of the same nature occur in the same region simultaneously, they result in interference. Interference of waves implies that the net effect ...

Sound Waves: Interference

Sound waves can be modeled either as longitudinal waves, wherein the molecules of the medium oscillate around an equilibrium position, or as pressure ...

Interference: Path Lengths

Consider two sources of sound, that may or may not be in phase, emitting waves at a single frequency, and consider the frequencies to be the same.
Two ...

/files/media/science-education/science-education-thumbs/14727.jpg

Sound Waves: Resonance

Resonance is produced depending on the boundary conditions imposed on a wave. Resonance can be produced in a string under tension with symmetrical ...

James Clerk Maxwell formulated a single theory combining all the electric and magnetic effects scientists knew during that time, calling the phenomena his ...

Electromagnetic waves are categorized according to their wavelengths and frequencies, giving the electromagnetic spectrum. These waves are classified as ...

Electromagnetic Wave Equation

Maxwell&#39;s equations for electromagnetic fields are related to source charges, either static or moving. These fields act on a test charge, whose ...

Propagation Speed of Electromagnetic Waves

Electromagnetic waves are consistent with Ampere&#39;s law. Assuming there is no conduction current Ampere&#39;s law is given as:


Consider a plane ...

Electromagnetic Waves in Matter

Electromagnetic waves can travel in the vacuum as well as in matter. For example light, which is an electromagnetic wave, can travel through air, water, ...

Energy Carried By Electromagnetic Waves

Anyone who has used a microwave oven knows there is energy in electromagnetic waves. Sometimes, this energy is obvious, such as in the summer sun&#39;s ...

Intensity Of Electromagnetic Waves

The energy transport per unit area per unit time, or the Poynting vector, gives the energy flux of an electromagnetic wave at any specific time. For a ...

Students who demonstrate understanding can evaluate the claims, evidence, and reasoning behind the idea that electromagnetic radiation can be described either by a wave model or a particle model and that for some situations one model is more useful than the other.  Clarifying Statement: Emphasis is on how the experimental evidence supports the claim and how a theory is generally modified in light of new evidence.  Examples of a phenomenon could include resonance, interference, diffraction, and photoelectric effect.  Assessment Boundry: Assessment does not include using quantum theory.

Electromagnetic Waves in Everyday Technology

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