Name: why light ejects electrons from metals
Uploaded: 2020-09-03T13:38:27.000Z
Duration: 2 min 26 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Physical Science

Waves and Electromagnetic Radiation

3.2.9-12.X

Photoelectric Effect

Lorsque la lumière d'une longueur d'onde et d'une fréquence particulières frappe un métal, des électrons sont éjectés du métal. Ce phénomène est connu comme l'effet photoélectrique. Cependant, seule la lumière au-dessus d'une fréquence de seuil peut éjecter des électrons du métal.La lumière de fréquence inférieure n'éjecte pas d'électrons, quelle que soit son intensité. Comment est-ce donc? Albert Einstein a proposé que la lumière se comporte comme un flux de particules ou de minuscules paquets.Un paquet ou quantum de lumière est appelé un photon. Chaque photon a une énergie, E, qui dépend de sa fréquence, nu. Les deux sont liés par cette équation, où h est la constante de Planck et a une valeur de 6, 626 fois 10 à la négative 34 joule-secondes.La lumière, et donc les photons, de fréquence plus élevée ont une plus grande énergie. Un électron est lié à un métal avec une énergie de liaison, phi. Ceci est également connu comme la fonction de travail du métal, W.Ainsi, une quantité d'énergie supérieure à W est nécessaire pour vaincre les forces d'attraction et de déloger l'électron.Lorsqu'un photon dont l'énergie est supérieure à W frappe le métal, son énergie excédentaire est transférée à l'électron sous forme d'énergie cinétique et l'électron est éjecté. Pour résumer l'effet photoélectrique, la lumière basse fréquence et longue longueur d'onde n'éjecte aucun électron du métal. L'augmentation de l'intensité de la lumière basse fréquence ne fait qu'augmenter le nombre de photons.Chaque photon a toujours la même énergie, ce qui ne suffit pas à déloger les électrons. La lumière de plus courte longueur d'onde, dont la fréquence est supérieure à la fréquence seuil, éjecte des électrons car chaque photon a une énergie supérieure. Plus la fréquence de la lumière augmente, plus l'énergie du photon augmente, et donc l'énergie cinétique de l'électron éjecté.Plus l'intensité de la lumière, plus les photons frappent le métal, et plus le nombre d'électrons qui sont éjectés. L'effet photoélectrique démontre le comportement des particules de la lumière.

effet photoélectrique

Lorsque la lumière d'une longueur d'onde particulière frappe une surface métallique, des électrons sont émis. C'est ce que l'on appelle l'effet photoélectrique. La fréquence minimale de la lumière qui peut causer une telle émission d'électrons est appelée la fréquence seuil, qui est spécifique au métal. La lumière dont la fréquence est inférieure à la fréquence seuil, même si elle est de haute intensité, ne peut pas déclencher l'émission d'électrons. Toutefois, lorsque la fréquence est supérieure à la valeur seuil, le nombre d'électrons éjectés est directement proportionnel à l'intensité du faisceau. 
 
 Selon la théorie ondulatoire classique, l'énergie d'une onde dépend de son intensité (qui dépend de son amplitude) et non de sa fréquence. Ces observations était en partie dues au fait qu'on pouvait voir le nombre d'électrons éjectés dans une période donnée augmenter à mesure que la luminosité augmentait. En 1905, Albert Einstein a été en mesure de résoudre le paradoxe en intégrant les résultats de quantification de Planck dans le modèle particulaire de la lumière qui était discrédité. 
 
 Einstein soutenait que les quantités finies d'énergie postulées par Planck pouvaient être appliquées à la lumière dans l'effet photoélectrique. La lumière frappant la surface métallique ne devait pas être considérée comme une onde, mais devait plutôt être considérée comme un flux de particules (plus tard appelées photons) dont l'énergie dépendait de leur fréquence ; la quantité d'énergie (E) dans un paquet de lumière dépend de sa fréquence (ν) selon l'équation suivante : 
 
 <img alt="Eq1" src="https://www.jovecore.com/CDNSource/lessons/976/976_Equations-01.png" style="height: 40px;" />
 
 où h est la constante de Planck. 
 
 L'effet photoélectrique peut être décrit en supposant que la lumière est quantifiée. Une certaine énergie minimale est nécessaire pour surmonter l'énergie de liaison (Φ) à laquelle un électron est soumis. Ceci est également appelé le travail d'extraction (W) du métal. 
 
 Comme les électrons dans le métal ont une certaine quantité d'énergie de liaison les maintenant là, la lumière incidente doit avoir plus d'énergie pour libérer les électrons. Les photons de la lumière basse fréquence ne contiennent pas assez d'énergie pour éjecter les électrons du métal. Même si le métal est exposé à une telle lumière pendant longtemps, aucune émission d'électrons n'est observée. Un électron ne peut être émis que lorsqu'un photon dont l'énergie est supérieure au travail d'extraction frappe le métal. 
 
 <img alt="Eq1" src="https://www.jovecore.com/CDNSource/lessons/976/976_Equations-02.png" style="height: 40px;" />
 
 L'énergie excédentaire du photon est convertie en énergie cinétique de l'électron émis. 
 
 <img alt="Eq1" src="https://www.jovecore.com/CDNSource/lessons/976/976_Equations-03.png" style="height: 40px;" />
 
 Par conséquent, les électrons sont éjectés lorsqu'ils sont frappés par des photons ayant une énergie suffisante (une fréquence supérieure au seuil). Plus la fréquence de la lumière incidente est élevée, plus l'énergie cinétique transmise lors des chocs aux électrons qui s'échappent est importante. Einstein a également soutenu que l'intensité lumineuse ne dépendait pas de l'amplitude de l'onde entrante, mais correspondait plutôt au nombre de photons frappant la surface dans une période donnée. Le nombre d'électrons éjectés augmente avec la luminosité. Plus le nombre de photons entrants est élevé, plus ils sont susceptibles d'entrer en collision avec certains des électrons. 
 
 L'effet photoélectrique suggère fortement le comportement particulaire de la lumière. Einstein a remporté le prix Nobel de physique en 1921 pour son explication de l'effet photoélectrique. Bien que de nombreux phénomènes de lumière puissent être expliqués en termes d'ondes ou de particules, certains phénomènes, tels que les motifs d'interférence obtenus lorsque la lumière passe par une double fente, étaient complètement contraires au point de vue particulaire de la lumière, tandis que d'autres phénomènes, tels que l'effet photoélectrique, étaient complètement contraires au point de vue ondulatoire de la lumière. En quelque sorte, à un niveau plus fondamental encore mal compris, la lumière se comporte à la fois comme une onde et comme une particule. C'est ce que l'on appelle la dualité onde-particule. 
 
 Ce texte est adapté de <a href="https://openstax.org/books/chemistry-2e/pages/6-1-electromagnetic-energy">Openstax, Chimie 2e, Section 6.1 : Énergie électromagnétique</a>.

Effet photoélectrique

Lorsqu’une lumière d’une longueur d’onde particulière frappe une surface métallique, des électrons sont émis. C’est ce qu’on appelle l’effet photoélectrique. La fréquence minimale de ...

Education

Enseignement

JoVE Core

Chemistry

Chimie

Electronic Structure of Atoms

Structure électronique des atomes

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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, of the beam.

Classical wave theory could not explain this result because it links a wave’s energy to its intensity, not its frequency. In 1905, Albert Einstein solved the problem by using Planck’s idea that energy is quantized. He treated light as a stream of particles called photons, and each photon carries energy based on its frequency.

A metal holds onto its electrons with a minimum amount of binding energy. This energy barrier is called the work function, or Φ, of the metal. Low-frequency photons do not have enough energy to overcome it, so no electrons are emitted even after long exposure. If a photon has more energy than the work function, the extra energy becomes kinetic energy of the escaping electron.

Higher-frequency light gives electrons more kinetic energy. Brightness also matters because intensity reflects the number of photons striking the surface in a given time. More photons increase the chance that some will hit electrons and free them.

The photoelectric effect supports the particle behavior of light. Einstein won the Nobel Prize in Physics in 1921 for explaining it. At the same time, other light behavior, such as the interference pattern in a double slit, does not fit a simple particle model. Together, these observations show wave-particle duality, the idea that light has both wavelike and particle-like properties.

Why Light Ejects Electrons from Metals

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

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

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 how light frees electrons from metals, why threshold frequency matters, and how Einstein’s photon idea explained the photoelectric effect.

Why Light Ejects Electrons from Metals | JoVE K12

chemistry

JoVE Core Chimie anime les concepts de chimie générale en utilisant des leçons vidéo concises et faciles à comprendre. De plus, nos vidéos de scientifiques à l'action présentent des expériences de recherche, classiques ou insolites, effectuées dans des laboratoires modernes du monde entier.

Louisiana Student Standards for Science

High School

motion-and-stability-forces-and-interactions

Motion And Stability: Forces And Interactions

HS-PS2-6

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Physics

Waves

Light phenomena

Tennessee Academic Standards

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

Waves and Their Applications in Technologies for Information Transfer

PHYS.PS4.7

CHEM1.PS4.1

Arizona Science Standards

HS+C.P1

HS+C.P1U1.2

Next Generation Science Standards

HS-PS4-4

Florida Department of Education

SC.912.P.8

SC.912.P.8.3

Texas Essential Knowledge and Skills

PHYS.9

PHYS.9.A

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

South Carolina College and Career Ready Science Standards

C-PS4-5

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-7.

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 ...

Electromagnetic Waves

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

The Electromagnetic Spectrum

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

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 ...

Momentum And Radiation Pressure

An object absorbing an electromagnetic wave would experience a force in the direction of propagation of the wave. This force occurs because ...

Radiation Pressure: Problem Solving

The radiation pressure applied by an electromagnetic wave on a perfectly absorbing surface equals the energy density of the wave. The wave&#39;s momentum ...

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.

3.2.9-12.V

Absorption of Radiation

The rate of heat transfer by emitted radiation is described by the Stefan-Boltzmann law of radiation:

where &#963; is the Stefan-Boltzmann constant, a ...

Students who demonstrate understanding can evaluate the validity and reliability of claims in published materials of the effects that different frequencies of electromagnetic radiation have when absorbed by matter.  Clarifying Statement: Emphasis is on the idea that photons associated with different frequencies of light have different energies, and the damage to living tissue from electromagnetic radiation depends on the energy of the radiation.  Examples of published materials could include trade books, magazines, web resources, videos, and other passages that may reflect bias.  Assessment Boundry: Assessment is limited to qualitative descriptions.

3.2.9-12.W

Energy Transfer in Chemical Reactions

Chemical reactions require sufficient energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ...

Dye-sensitized Solar Cells

Source: Tamara M. Powers, Department of Chemistry, Texas A&#38;M University
Today&#39;s modern world requires the use of a large amount of energy. While ...

The Wave Nature of Light

The nature of light has been a subject of inquiry since antiquity. In the seventeenth century, Isaac Newton performed experiments with lenses and prisms ...

The electromagnetic spectrum consists of all the types of electromagnetic radiation arranged according to their frequency and wavelength. Each of the ...

When light of a particular wavelength strikes a metal surface, electrons are emitted. This is called the photoelectric effect. The minimum frequency of ...

dual-nature-of-electromagnetic-em-radiation

Dual Nature of Electromagnetic (EM) Radiation

Electromagnetic (EM) radiation consists of electric and magnetic field components oscillating in planes perpendicular to each other and mutually ...

interaction-of-em-radiation-with-matter-spectroscopy

Interaction of EM Radiation with Matter: Spectroscopy

Electromagnetic (EM) radiation can be considered an oscillating electric and magnetic field propagating through a medium that can interact with matter in ...

molecular-spectroscopy-absorption-and-emission

Molecular Spectroscopy: Absorption and Emission

Molecules possess discrete energy levels called quantum states. Unlike atoms, which have simpler energy levels, molecules possess additional rotational ...

Spectrophotometry: Introduction

Spectrophotometry is the quantitative measurement of the absorption, reflection, diffraction, or transmission of electromagnetic radiation through a ...

ultraviolet-and-visible-uvvis-spectroscopy-overview

Ultraviolet and Visible (UV&ndash;Vis) Spectroscopy: Overview

Ultraviolet&#8211;visible (UV&#8211;visible or UV&#8211;Vis) spectroscopy is an analytical technique that investigates the interaction between matter and ...

Infrared (IR) Spectroscopy: Overview

When electromagnetic radiation passes through a material, atoms or molecules transition from a lower to a higher energy state by absorbing radiation ...

Raman Spectroscopy: Overview

The underlying principle of Raman spectroscopy is based on the interaction between light and matter, specifically molecules&#39; inelastic scattering of ...

Atomic Absorption Spectroscopy: Overview

Atomic absorption spectroscopy (AAS) is a technique used to analyze elements by measuring electromagnetic radiation (EMR) absorbed by atoms, which causes ...

Nuclear Magnetic Resonance (NMR): Overview

Nuclear magnetic resonance (NMR) is a phenomenon exhibited by certain nuclei that can absorb characteristic radio frequency radiation under certain ...

Students who demonstrate understanding can communicate technical information about how some technological devices use the principles of wave behavior and wave interactions with matter to transmit and capture information and energy.  Clarifying Statement: Examples could include solar cells capturing light and converting it to electricity; medical imaging; and communications technology.  Assessment Boundry: Assessments are limited to qualitative information.  Assessments do not include band theory.

Why Light Ejects Electrons from Metals

Description

Transcript

Tags

More videos by Standards