Name: electromagnetic waves: uses across the spectrum
Uploaded: 2020-09-03T13:38:27.000Z
Duration: 2 min 37 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Earth and Space Science

Earth's Systems

3.3.9-12.H

The Electromagnetic Spectrum

电磁频谱是电磁辐射的 频率范围和相应的波长。波长和频率互相 成反比；波长越长，频率越低。电磁辐射的能量 与其频率成正比，如普朗克方程所示。因此，能量最高的电磁波 具有最短的波长。电磁波可以分为 无线电波、微波、红外线、可见光、紫外线、X 射线或伽马射线，取决于它们的频率和波长。用于在通信系统之间传输信号的 无线电波，具有最长的波长、最低的频率和最少的能量。微波的波长是第二长的。它们的用途从雷达系统 到在家加热食物。接下来是红外线辐射，它是 由温暖物体发出的热辐射的 重要组成部分。例如，地球既吸收了作为太阳辐射能量 一部分的红外线辐射，同时它本身又将红外线辐射发射到太空中。可见光的波长更短，从 740 到 390 纳米不等。红光的波长最长，紫光的波长最短。人类的眼睛只对这个狭窄的波长范围 有反应。紫外线辐射的波长更短。阳光是最常见的 紫外线辐射源，它具有 足够的能量，因此过度的暴露会导致晒伤 并导致皮肤癌。X 射线和伽马射线的波长最短 而且是电磁辐射中能量最强的形式。X 射线可以穿透许多物质，但它们不容易穿透骨骼。这使它们成为一种重要的成像工具。伽马射线最为人所知的是它们是 在某些放射性元素的衰变链中 释放出来的。虽然伽马射线和 X 射线之间没有普遍的 区别，但伽马射线通常 被认为具有最短的波长、最高的 频率和最高的能量。

电磁频谱

电磁光谱由根据其频率和波长排列的所有类型的电磁辐射组成。可见光的每种颜色都有特定的频率和与之相关的波长，您可以看到可见光仅占电磁光谱的一小部分。由于开发用于电磁频谱各个部分的技术不同，出于方便和历史遗留的原因，通常将不同的单位用于频谱的不同部分。例如，通常将无线电波指定为频率（通常以MHz兆赫兹为单位），而通常将可见光区域指定为波长（通常以nm纳米或angstrom Å埃为单位）。
 
 <img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/975/975Image_1.png" style="width: 700px;" /> 
 图1：电磁频谱的各个部分按频率递增和波长递减的顺序显示。
 
 电磁波的类型包括无线电波、微波、紫外线、可见光、红外线、x射线和伽马射线。
 
 无线电波具有最长的波长，最低的频率，并且携带的能量最少。它们用于手机技术、广播电视广播、空中交通管制等。
 
 与无线电波相比，微波的波长更短。它们会被水吸收并用于加热和烹饪食物。
 
 接下来是红外线，它是由温暖的物体发出的。例如，地球从太阳吸收辐射能并发出红外辐射。大气吸收并重新发射一些红外辐射，以通过温室效应维持地球的平均温度。夜视镜可感知人体发出的红外辐射。
 
 可见光只是740至390 nm纳米范围内电磁辐射的一小部分。人眼只能看到这一小范围的波长。可见光主要由七种颜色组成，包括红色、橙色、黄色、绿色、蓝色、靛蓝和紫色。
 
 紫外线辐射的波长范围为400至10 nm 纳米。阳光是最常见的紫外线辐射源。它携带足够的能量，过度暴露会导致晒伤。
 
 X射线可以穿过许多物质，使其成为重要的成像工具。牙医将X射线用于诊断目的，而机场安检则使用X射线对手提箱中的组件进行可视化。
 
 伽玛射线具有较小的波长，较高的频率和能量。伽玛射线是通过核反应和自然产生的放射性元素释放的。
 
 X射线和伽马射线是电磁辐射的最活跃形式。它们的高能量可以使原子和分子电离。电离辐射可导致永久性变化或对生物分子的破坏。它们被用来破坏癌细胞。 ＆nbsp; ＆nbsp; 
 
 本文改编自<a href="https://openstax.org/books/chemistry-2e/pages/6-1-electromagnetic-energy"> Openstax，化学2e，第6.1节：电磁能量。</a>

电磁波谱包含所有类型的电磁辐射，按照其频率和波长进行排列。每一种……

Education

教育

JoVE Core

Chemistry

化学

Electronic Structure of Atoms

原子的电子结构

KEY TERMS AND CONCEPTS

关键术语与概念

electromagnetic waves: uses across the spectrum

The electromagnetic spectrum includes all electromagnetic radiation arranged by frequency and wavelength. Visible light is only a small part of it, and each color of visible light has its own frequency and wavelength. Different parts of the spectrum also use different units. Radio waves are usually measured in MHz, while the visible range is often measured in nm or angstroms.

The spectrum is organized from radio waves to gamma rays as frequency increases and wavelength decreases. Radio waves have the longest wavelengths, the lowest frequencies, and the least energy. They are used in cell phones, radio and television broadcasts, and air-traffic control. Microwaves have shorter wavelengths than radio waves and are absorbed by water, which is why they can heat and cook food.

Infrared radiation is next and is emitted by warm objects. The Earth absorbs energy from the Sun and gives off infrared radiation. Some of this radiation is absorbed and re-emitted by the atmosphere, which helps keep Earth’s average temperature stable through the greenhouse effect. Night vision goggles also detect the infrared radiation that our bodies emit.

Visible light spans only about 740 to 390 nm, so the human eye can see just a narrow band of electromagnetic radiation. This band includes red, orange, yellow, green, blue, indigo, and violet. Ultraviolet radiation has wavelengths from about 400 to 10 nm. Sunlight is the most familiar source of UV radiation, and too much exposure can cause sunburn.

X-rays can pass through many materials, so they are useful for imaging. Dentists use x-rays for diagnosis, and airport security uses them to view what is inside a suitcase. Gamma rays have even smaller wavelengths, higher frequencies, and higher energies. They come from nuclear reactions and naturally occurring radioactive elements. X-rays and gamma rays are the most energetic forms of electromagnetic radiation, and their ionizing radiation can damage biological molecules. Because of that, they can be used to destroy cancer cells.

Electromagnetic Waves: Uses Across the Spectrum

electromagnetic-waves-uses-across-the-spectrum

the wave nature of light

Measuring Light with Wavelength and Frequency

Light can be described as an electromagnetic wave, and its behavior helps explain many patterns seen in science. For centuries, scientists have tried to understand light. Newton used lenses and prisms to show that white light is made of the colors of the rainbow mixed together. He explained light as tiny particles moving at high speed. Other scientists, including Christiaan Huygens, showed that reflection and refraction could also be explained by treating light as a wave. At the time, people...

the electromagnetic spectrum

The electromagnetic spectrum includes all electromagnetic radiation arranged by frequency and wavelength. Visible light is only a small part of it, and each color of visible light has its own frequency and wavelength. Different parts of the spectrum also use different units. Radio waves are usually measured in MHz, while the visible range is often measured in nm or angstroms. The spectrum is organized from radio waves to gamma rays as frequency increases and wavelength decreases. Radio waves...

interference and diffraction

Wave Patterns from Light and Slits

Light can form wave patterns through interference and diffraction. When two electromagnetic waves meet with their peaks and troughs lined up, they combine into a larger wave. This is constructive interference, and the waves are in phase. When a peak of one wave meets a trough of the other, the waves reduce each other. This is destructive interference, and the result has a much lower amplitude. Diffraction is another wave behavior. When light passes through a slit that is about the same size as...

photoelectric effect

Why Light Ejects Electrons from Metals

Light can eject electrons from a metal surface when it has the right frequency. This process is called the photoelectric effect. Each metal has its own threshold frequency, which is the minimum light frequency needed to free electrons. Light below the threshold frequency cannot cause emission, even if it is very bright. When the light frequency is above the threshold, electrons are ejected. In that case, the number of electrons released is directly proportional to the intensity, or brightness,...

the bohr model

Bohr’s Quantized Atomic Orbits

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emission spectra

Line Spectra from Heated Gases

Line spectra are produced when heated gases give off light at specific wavelengths. In contrast, hot solids, liquids, or condensed gases radiate excess energy as a continuous spectrum. That spectrum contains an unbroken range of wavelengths. A gas at low partial pressure can produce a line spectrum when it is excited by an electric current or heated. Fluorescent light bulbs and neon signs work in this way. Each element has its own characteristic set of lines, and molecules can also produce...

the de broglie wavelength

Electron Waves and Standing Orbits

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the uncertainty principle

Electron Position and Momentum Limits

Heisenberg’s uncertainty principle sets a limit on how precisely we can know an electron’s position and momentum at the same time. Momentum is the motion of a particle, and the two measurements affect each other. If the momentum is known more accurately, the position becomes less certain, and the reverse is also true. Heisenberg described this limit with an equation that uses Planck’s constant. The equation shows the smallest possible uncertainty for position and momentum together. It explains...

the quantum-mechanical model of an atom

Electron Orbitals in Quantum Mechanics

Quantum mechanics explains how electrons behave in atoms using waves and probability. Erwin Schrödinger built on de Broglie’s idea that an electron in hydrogen could act like a circular standing wave instead of moving in fixed circular paths. He then derived the Schrödinger equation, which became a major step in modern atomic theory. When Schrödinger applied his equation to hydrogen-like atoms, it matched Bohr’s energy expression and the Rydberg formula for hydrogen spectra. He described...

quantum numbers

Electron Orbitals and Spin

Electron orbitals are described by quantum numbers that show where an electron is most likely to be found around the nucleus. These numbers come from the quantum mechanical model, which is based on solutions of the Schrödinger equation. They also help explain why electron energy comes in set values instead of changing smoothly. The principal quantum number, n, labels the energy level. It can be 1, 2, 3, and so on, and higher n values usually mean higher electron energy. This number also tells...

atomic orbitals

Electron Regions in Atomic Orbitals

Electron regions in atomic orbitals show where an electron is most likely to be found in an atom. These three-dimensional regions are often drawn as boundary surfaces around the densest part of the cloud. The shape of an orbital depends on the angular momentum quantum number, l. This value can range from 0 to n - 1, where n is the principal quantum number. For n = 1, only l = 0 is allowed. For n = 2, both l = 0 and l = 1 are allowed. Orbitals with the same value of l form a subshell. The l =...

the pauli exclusion principle

Electron Spin and Orbital Pairing

Electron spin and orbital pairing explain why only two electrons can fit in one atomic orbital. Electron configuration describes how electrons are arranged in an atom’s orbitals. It is written with three parts: the principal quantum number, n, the orbital type, or subshell, and a superscript that shows how many electrons are in that subshell. For example, 2p4 means four electrons in a p subshell with n = 2, and 3d8 means eight electrons in a d subshell with n = 3. The three quantum numbers...

the energies of atomic orbitals

Shielding and Orbital Penetration

Shielding and orbital penetration help explain why electrons in an atom have different energies. Electrons are attracted to the positive nucleus, but they also repel one another in atoms with more than one electron. The strength of these forces depends on the charge and the distance between the particles. Opposite charges attract, like charges repel, and the force gets weaker as the particles move farther apart. An electron that stays closer to the nucleus is held more tightly. That means...

the aufbau principle and hund's rule

Electron Filling Order in Atomic Orbitals

Electron filling order in atomic orbitals follows the aufbau principle and Hund's rule. To write an electron configuration, we build atoms in order of atomic number. Starting with hydrogen and moving across the periods of the periodic table, one proton is added to the nucleus and one electron is placed into the correct subshell. This process describes the ground-state electron configurations of the elements. The aufbau principle comes from the German word aufbau, which means "to build up." It...

electron configuration of multielectron atoms

electron-configuration-of-multielectron-atoms

Valence Electrons and Noble Gas Shorthand

Valence electrons and noble gas shorthand help show how electrons are arranged in multielectron atoms. Sodium, the alkali metal with atomic number 11, has one more electron than neon. That extra electron goes into the lowest-energy subshell available, the 3s orbital, so sodium has the configuration 1s2 2s2 2p6 3s1. Electrons in the outermost shell, where n is highest, are called valence electrons. Electrons in the inner shells are called core electrons. Because core electrons often match a...

key terms and concepts

Explore the electromagnetic spectrum from radio waves to gamma rays, including visible light, infrared, UV, X-rays, and their real-world uses.

Electromagnetic Waves: Uses Across the Spectrum | JoVE K12

chemistry

JoVE Core 化学通过简单明了且通俗易懂的动画视频课程，将普通化学概念带入到现实生活当中。此外，在科学家行动视频中，我们演示了在实验室中进行的经典和原始研究实验。

Weather and Climate

3.3.9-12.E

Physical Science

Waves and Electromagnetic Radiation

3.2.9-12.X

Louisiana Student Standards for Science

High School

Earth Science

Earth’s Systems

HS-ESS2-4

Tennessee Academic Standards

Physics

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

Waves and Their Applications in Technologies for Information Transfer

PHYS.PS4.7

PHYS.PS4.8

Arizona Science Standards

HS+C.P1

HS+C.P1U1.2

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

New Jersey Student Learning Standards for Science

HS-PS4-4

Alabama Course of Study Science

Matter and Its Interactions

9-12.C.1.1.c

Earth's Place in the Universe

9-12.ESS.1.2

9-12.ESS.1.2.a

Next Generation Science Standards

Florida Department of Education

SC.912.E.5

SC.912.E.5.8

SC.912.P.8

SC.912.P.8.3

SC.912.P.10

SC.912.P.10.19

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

South Carolina College and Career Ready Science Standards

C-PS4-4

C-PS4-5

P-PS4-4

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-7.

HS. Waves and Electromagnetic Radiation

HS-PS4-3.

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Students who demonstrate understanding can develop a model based on evidence of Earth's interior to describe the cycling of matter by thermal convection.  Clarification Statement: Emphasis is on both a one-dimensional model of Earth, with radial layers determined by density, and a three-dimensional model, which is controlled by mantle convection and the resulting plate tectonics.  Examples of evidence include maps of Earth's three-dimensional structure obtained from seismic waves, records of the rate of change of Earth's magnetic field (as constraints on convection in the outer core), and identification of the composition of Earth's layers from high-pressure laboratory experiments.  Assessment Boundary:

3.3.9-12.I

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3.3.9-12.K

Electromagnetic Waves: Uses Across the Spectrum

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