JCP321H5 Lecture Notes - Lecture 3: Matter Wave, Electron Diffraction, Elastic Collision

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15 Oct 2018

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Photoelectric effect

Relevance

What is it?

the emission of electron when a beam

of light is shone on a material.

How does it work?

here is what the photoelectric effect

looks like:

Put simply, it's an elastic collision

between a photon of light and an

electron

The amount of energy needed to

dislodge an electron is equal to

Planck’s constant times the frequency

of the light:

● As a result, red light, no matter

how intense, cannot eject an

electron. This is because red

light doesn't have enough

energy to do so

What is it used for?

Solar power

Photosynthesis

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Why is it important?

It is one of the very few things that light

does that strictly suggests a particle

nature

Here is a graph of some of the earliest data taken on the photoelectric effect:

Photon

Relevance

What is it?

A packet of a light wave (if that makes

any sense)

How does it work?

Photons have energy:

The energy of a photon is equal to

Planck’s constant times the frequency

Photons also have momentum:

The momentum of the light is inversely

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Document Summary

Relevance the emission of electron when a beam of light is shone on a material. here is what the photoelectric effect looks like: Put simply, it"s an elastic collision between a photon of light and an electron. The amount of energy needed to dislodge an electron is equal to. Planck"s constant times the frequency of the light: As a result, red light, no matter how intense, cannot eject an electron. This is because red light doesn"t have enough energy to do so. It is one of the very few things that light does that strictly suggests a particle nature. Here is a graph of some of the earliest data taken on the photoelectric effect: A packet of a light wave (if that makes any sense) The energy of a photon is equal to. Why is it important? proportional to the wavelength of the light.

Related Questions

Molybdenum metal must absorb radiation with a minimum frequency of 1.09 × 10¹⁵ s^{- 1} before it can eject an electron from its surface via the photoelectric effect. (a) What is the minimum energy needed to eject an electron? (b) What wavelength of radiation will provide a photon of this energy? (c) If molybdenum is irradiated with light of wavelength of 120 nm, what is the maximum possible kinetic energy of the emitted electrons?

jadegerbil920

1. The energy needed to dissociate an oxygen molecule into oxygenatoms (the bond energy) is 498 k,J / mol. What is the maximumwavelength of light that will initiate the split of oxygenmolecule? Is visible light capable to complete thisprocess?<?xml:namespace prefix = o ns ="urn:schemas-microsoft-com:office:office" />

2.In the potassium emission spectrum quite intense line isobserved at 766.0 nm. Calculate the frequency of radiationproducing this line. Is this line visible to the eye? If yourprevious answer is yes, what is the color of this line? If not, isit at higher or lower energy than visible light? (c = 2.998x 10⁸m/s; R = 3.2881 x 10¹⁵1/s)

3. Find the energy change when an electron moves from the n = 4level to the

n = 2 level in thehydrogen atom. If this energy is emitted as a photon, what is thewavelength of this photon? (c = 2.998 x 10⁸m/s; R = 3.2881x 10¹⁵1/s)

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LIGHT LAB SPRING 2018 CHEM 1430 Ill. Quantization of Electromagnetic Radiation In 1894, the German physidist, Max Plank, was working for a utility company to maximize visible light output from incandescent lamps using minimum power. Based on theoretical considerations, Planck postulated that electromagnetic energy could only be emitted at discrete values, rather than the continuum of predicted by classical physics, as multiples of the frequency of the radiation. Planck's Postulate took the mathematical form: EÂ·hv where the energy emitted, in Joules, is the product of a constant, h, known as Planck's Constant, and the frequency of the radiation, v. Planck's Postulate was experimentally verified and h found to have the value of 6.626 x 1034 Js(Joule seconds). The idea that electromagnetic radiation energy had specific frequency dependent energy was termed a "quantum of action," a distressing finding for the dlassically trained Planck. Despite his objections, Planck adopted this quantization of energy as a last resort to reconcile experiment with theory. This discovery set the stage for the early understanding of atomic structure, led to the term "photon" to describe the packet of energy carried by light waves, led to an understanding of the photoelectric effect, eventually leading to the development of general quantum theory Planck's Relationship, in combination with the tight equation, c the energy of a photon from frequency or wavelength. Î» w, allow expressions to be written to calculate ACTIVITY 4: QUANTIZATION OF THE ENERGY OF RADIATION To practice cakculations with Planck's Relationship, complete the following table, showing work with units in the right mest column, Convert given frequency to energy or given wavelength to energy. Take the value for Planck's Constant, h, to be 6.626 x 10"Js, show a calculation string include dimensions, reporting the final value to the proper number of significant figures Spectral Region Wavelength Frequency Energy in J/photon Show Calculation String Î» in meters v in s or cps X-ray 6.0 x 10"m Blue light 4.5 x 10m Infrared 4.1 x 10" cps Microwave 7.3 x 101 cps Radio Wave 3.0x 10 m IV. Bohr's Quantum Model for the Hydrogen Atom Ernest Rutherford's Gold Foil Experiment of 1911 demonstrated the nuclear structure of the atom. Questions remained as to how electrons were arranged in the atom. The most common belief called for the negatively charged the late 19h century recognized a particle (an electron) traveling around a body (the positively charged nucleus) would continuously radiate energy, slowing over time, eventually falling into the nucleus. Matter would collapse. Page 8 of 12

JCP321H5 Lecture Notes - Lecture 3: Matter Wave, Electron Diffraction, Elastic Collision

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