Name: measuring light with wavelength and frequency
Uploaded: 2020-09-03T13:38:27.000Z
Duration: 2 min 12 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry and Physics

IPC.7

IPC.7.E

The Wave Nature of Light

Солнечный свет, микроволны, используемые для приготовления пищи, и радиоволны, излучаемые маршрутизаторами Wi-Fi, все это примеры электромагнитного излучения. Электромагнитное излучение это передача энергии, исходящей от движения электрически заряженных частиц. Это движение создает перпендикулярные колеблющиеся электрические и магнитные поля, распространяющиеся в пространстве в виде волн.Как и все волны, электромагнитные волны характеризуются амплитудой, длиной волны и частотой. Пиковая амплитуда это расстояние от средней линии до пика или впадины волны. Она определяет интенсивность волны.Например, амплитуда видимого света связана с его яркостью;чем больше амплитуда, тем ярче или интенсивнее свет. Длина волны это расстояние между идентичными точками на соседних волнах, такими как последовательные пики или впадины;она обозначается греческой буквой лямбда. Электромагнитное излучение можно классифицировать по длине волны, которая может варьироваться от километров до пикометров.Например, диапазон длины волн видимого света составляет от 400 до 750 нанометров, что соответствует фиолетовому и красному свету соответственно. Частота, обозначаемая греческой буквой ню, это количество волн, которые проходят через контрольную точку за одну секунду, и измеряется в герцах или циклах в секунду. Длина волны это ширина одного цикла.Скорость волны это произведение ее частоты и длины. Следовательно, частота волны прямо пропорциональна скорости, с которой волна распространяется. Однако она обратно пропорциональна длине волны.Таким образом, длинные волны, например радиоволны, имеют низкие частоты. Эти волны имеют меньшую энергию, чем волны с высокими частотами и короткими длинами, такие как гамма-лучи.

Волновая природа света

Природа света была предметом исследования с древности. В семнадцатом веке Исаак Ньютон проводил эксперименты с линзами и призмами и смог продемонстрировать, что белый свет состоит из отдельных цветов радуги, Объединенных вместе. Ньютон объяснил свои оптические выводы с точки зрения “корпускулярной” природы света,причём свет был представлен потоками крайне мелких частиц, перемещающихся на высоких скоростях в соответствии с законами движения Ньютона.  
 
 Другие учёные в семнадцатом веке, такие как Кристиан Гюйгенс, показали, что такие оптические явления, как отражение и преломление, могут быть в равной степени хорошо объяснены с точки зрения света, как волны, перемещающие с высокой скоростью через среду, называемую «светоносным эфиром», который, как считалось, проникает во все пространство. В начале девятнадцатого века Томас Янг продемонстрировал, что свет, проходящий через узкие, близко расположенные прорези, произвел помехи, которые нельзя объяснить с точки зрения ньютоновских частиц, но их можно легко объяснить волнами. Позднее в девятнадцатом веке, после того как Джеймс Клерк Максвелл разработал свою теорию электромагнитного излучения и показал, что свет является видимой частью обширного спектра электромагнитных волн, точка зрения частиц на свет была полностью дискредитирована.  
 
 К концу девятнадцатого века ученые рассматривали физическую вселенную как состоящую из двух отдельных областей: вещества, состоящие из частиц, движущихся в соответствии с законами движения Ньютона, и электромагнитного излучения, состоящего из волн, управляемых уравнениями Максвелла. Сегодня эти области называют классической механикой и классической электродинамикой (или классическим электромагнетизмом). Хотя было несколько физических явлений, которые нельзя было объяснить в рамках этой теории, ученые в то время были настолько уверены в общей надежности этой парадигмы, что рассматривали эти аберрации как загадочные парадоксы, которые в конечном итоге каким-то образом разрешатся в рамках этой структуры. Эти парадоксы привели к современной теории, которая тесно связывает частицы и волны на фундаментальном уровне, называемом дуальностью волна-частица, которая вытеснила классический взгляд. 
 
 Видимый свет и другие формы электромагнитного излучения играют важную роль в химии, так как их можно использовать для передачи энергии электронов в атомах и молекулах. Большая часть современных технологий основана на электромагнитном излучении. Например, радиоволны с мобильного телефона, рентгеновские лучи, используемые стоматологами, энергия, используемая для приготовления пищи в микроволновой печи, тепловое излучение от красных горячих предметов и свет с экрана телевизора являются формами электромагнитного излучения, которые все проявляют волнообразное поведение. 
 
 <h4>Волны </h4>
 
 Волна — это колебание или периодическое движение, которое может транспортировать энергию из одной точки в пространстве в другую. Вокруг нас есть масса примеров волн. Встряхивание конца каната переносит энергию от руки к другому концу каната, при падении гальки в пруд волны будут распространяться в стороны вдоль поверхности воды, а расширение воздуха, сопровождающее удар молнии, создает звуковые волны (гром), которые могут перемещаться в направлении на несколько миль. В каждом из этих случаев кинетическая энергия передается через вещество (канат, воду или воздух), в то время как вещество остается в силе.  
 
 Волны не обязательно должны быть ограничены в прохождении через материю. Как показал Максвелл, электромагнитные волны состоят из электрического поля, качающегося в шаге с перпендикулярным магнитным полем, оба из которых перпендикулярны направлению движения. Эти волны могут проходить через вакуум с постоянной скоростью 2.998 × 108 м/с, скоростью света (обозначается буквой c). 
 
 Все волны, в том числе формы электромагнитного излучения, характеризуются длиной волны (обозначаемой λ, строчной греческой буквой лямбда), частотой (обозначаемой ν, строчной греческой буквой nu) и амплитудой.  
 
 Длина волны — это расстояние между двумя последовательными пиками или ложбинами в волне (измеряется в метрах в системе СИ). Электромагнитные волны имеют длины волн, которые находятся в пределах огромного диапазона длин волн от километров (103 м) до пикометров (10-12 м). Частота — это количество циклов, которые проходят через определенную точку в пространстве за определенный промежуток времени (в системе СИ это измеряется в секундах). Цикл соответствует одной полной длине волны. Единица измерения частоты, выраженная в циклах в секунду [s-1], — герц (Гц). Наиболее распространенными кратными единицей являются мегагерц (1 МГц = 1 × 106 Гц) и гигагерц (1 ГГц = 1 × 109 Гц).  
 
 Амплитуда соответствует величине смещения волны, и это соответствует половине высоты между пиками и ложбинами. Амплитуда связана с интенсивностью волны, которая для света является яркостью, а для звука — громкостью. Произведение длины волны (λ) и ее частоты (ν), λν, является скоростью волны. Таким образом, для электромагнитного излучения в вакууме скорость равна основной константе, c: 
 
 <img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/974/974_Equations-01.png" style="height: 40px;" />
 
 Длина волны и частота обратно пропорциональны: По мере увеличения длины волны частота уменьшается. Спектр электромагнитного излучения — это диапазон всех типов электромагнитного излучения.  
 
 Этот текст адаптирован из <a href="https://openstax.org/books/chemistry-2e/pages/6-1-electromagnetic-energy">Openstax, Химия 2е изд., раздел 6.1: Электромагнитная энергия.</a>

Природа света была предметом исследования с глубокой древности. В семнадцатом веке Исаак Ньютон проводил эксперименты с линзами и призмами...

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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 imagined these waves traveling through a medium called luminiferous aether, which was thought to fill all space. In the early 1800s, Thomas Young showed that light passing through two narrow slits makes an interference pattern. That result fit the wave model much better than the particle model.

James Clerk Maxwell later developed electromagnetic theory and showed that visible light is part of a much larger spectrum of electromagnetic waves. By the end of the nineteenth century, many scientists accepted a split view of the physical world. Matter was described as particles, while electromagnetic radiation was described as waves. These ideas are now called classical mechanics and classical electrodynamics, or classical electromagnetism.

Some experimental results did not fit that classical picture. Scientists first saw them as strange puzzles that might still be solved within the old framework. Those puzzles eventually led to wave-particle duality, a modern idea that links waves and particles at a basic level. This idea replaced the older view.

Electromagnetic radiation matters in chemistry because it can help reveal the energies of electrons in atoms and molecules. It also powers many technologies. Radio waves from a mobile phone, X-rays used by dentists, microwave energy used to cook food, radiant heat from red-hot objects, and the light from a television screen are all forms of electromagnetic radiation. Each of these shows wavelike behavior.

A wave is an oscillation, or repeating motion, that carries energy from one place to another. Rope waves, ripples on water after a pebble falls in, and sound waves from thunder are common examples. In these cases, energy moves through the rope, water, or air while the material itself stays mostly in place. Waves do not have to travel through matter, because electromagnetic waves can move through empty space.

Maxwell showed that electromagnetic waves contain an electric field and a magnetic field that oscillate together. These fields are perpendicular to each other and to the direction the wave travels. In a vacuum, electromagnetic waves move at 2.998 × 10^8 m/s, which is the speed of light, c. Like all waves, they are described by wavelength, frequency, and amplitude.

Wavelength is the distance between two peaks or two troughs. Frequency is the number of wave cycles that pass a point in a given time. Amplitude is the size of the wave’s displacement, which is half the height between a peak and a trough. Amplitude is related to intensity, so for light it affects brightness, and for sound it affects loudness. Wavelength and frequency are linked by the equation λν = speed, so in a vacuum c = λν. As wavelength increases, frequency decreases. Electromagnetic waves span a huge range, from kilometers to picometers, and the full set is called the electromagnetic spectrum.

Measuring Light with Wavelength and Frequency

measuring-light-with-wavelength-and-frequency

the wave nature of light

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

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...

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

Bohr’s quantized atomic orbits explain why hydrogen atoms can stay stable. Early in the twentieth century, Ernest Rutherford and his colleagues described atoms as tiny dense nuclei with lighter electrons moving around them. This picture was called the planetary model because it compared the atom to a miniature solar system, with electrons orbiting the nucleus like planets around the sun. The simplest atom is hydrogen. It has one proton in the nucleus and one electron moving around it. In the...

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

Electron waves and standing orbits explain how tiny particles can behave like waves. Large objects in the macroscopic world, like a billiard ball on a table, follow classical physics. A ball keeps moving in a straight line unless it hits another ball or a force such as friction acts on it. It also has a well-defined position, velocity, and momentum, where momentum is mass times velocity. Waves behave differently from macroscopic particles. When waves interact, they can form interference...

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 light as an electromagnetic wave, including wavelength, frequency, amplitude, the speed of light, and examples from the electromagnetic spectrum.

Measuring Light with Wavelength and Frequency | JoVE K12

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JoVE Core Chemistry brings general chemistry concepts to life using concise and easy-to-understand animated video lessons. Plus, in the scientist-in-action videos, we demonstrate classical and original research experiments performed in today's laboratories worldwide.

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South Carolina College and Career Ready Science Standards

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New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-7.

HS. Waves and Electromagnetic Radiation

HS-PS4-3.

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Subatomic Particles

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Elements: Chemical Symbols and Isotopes

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Ions and Ionic Charges

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The Periodic Table

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Atomic Mass

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Molar Mass

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Periodic Classification of the Elements

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Types of Chemical Bonds

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Ionic Bonding and Electron Transfer

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The Born-Haber Cycle

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Covalent Bonding and Lewis Structures

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Electronegativity

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Bond Polarity, Dipole Moment, and Percent Ionic Character

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Bond Energies and Bond Lengths

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Bonding in Metals

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Model basic atomic structure and relate an element's atomic structure to its bonding, reactivity, and placement on the Periodic Table.

IPC.7.A

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Physical and Chemical Properties of Matter

The characteristics that enable us to distinguish one substance from another are called properties.

Physical Properties of Matter

A physical property is ...

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Atomic Radii and Effective Nuclear Charge

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Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it ...

Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Alkali Metals

Group 1 elements are soft and shiny metallic solids. They are malleable, ductile, and good conductors of heat and electricity. The melting points of the ...

Use patterns within the Periodic Table to predict the relative physical and chemical properties of elements.

IPC.7.B

Science concepts. The student knows that relationships exist between the structure and properties of matter. The student is expected to:

Measuring Light with Wavelength and Frequency

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