Electromagnetic SpectrumElectromagnetic Spectrum

Quantum MechanicsQuantum MechanicsAt the conclusion of our time At the conclusion of our time

together, you should be able to:together, you should be able to:

Define the EMS (electromagnetic spectrum.

List the various parts of a wave of electromagnetic radiation

Explain how this radiation is “quantized” by the electrons in an atom.

Use this information to determine an unknown element with a flame test.

EMSEMS

Made up of electromagnetic radiationMade up of electromagnetic radiationForm of Form of energyenergyBehaves like a Behaves like a wavewave

Kinds of radiation are:Kinds of radiation are:

Gamma RaysGamma Rays X RaysX Rays Ultraviolet RaysUltraviolet Rays VISIBLE LIGHTVISIBLE LIGHT InfraredInfrared MicrowaveMicrowave Radio WavesRadio Waves

Electromagnetic Radiation

Kinds of Radiation are:Kinds of Radiation are:

Features of WavesFeatures of Waves

Have repetitive motionHave repetitive motion Characterized by four properties:Characterized by four properties:

WavelengthWavelength FrequencyFrequency AmplitudeAmplitude SpeedSpeed

Wavelength (Wavelength (גג))

One full cycle of a waveOne full cycle of a wave Crest to Crest or Trough to TroughCrest to Crest or Trough to Trough Wavelengths of visible light areWavelengths of visible light are

400 – 750400 – 750 nanometers nanometers Violet Light = Violet Light = short short wavelengthwavelength

high high frequencyfrequency Red Light = Red Light = longlong wavelength wavelength

low low frequencyfrequency

Frequency (v)Frequency (v)

The number of cycles (one upward The number of cycles (one upward and downward motion) a wave and downward motion) a wave completes in one second.completes in one second.

Speed of light – is a constant (c)Speed of light – is a constant (c) Speed = Speed = 3.0 x 103.0 x 1088 meters per meters per

second (in air)second (in air) Waves travel slower through other Waves travel slower through other

types of types of mattermatter

AmplitudeAmplitude

Height of a waveHeight of a wave Measured from origin to peakMeasured from origin to peak

Relationship between (Relationship between (גג and v)and v)

C = ( C = ( גג ) x (v)) x (v)

Where:Where:

c = c = speed of lightspeed of light

wavelengthwavelength = = גג

v = v = frequencyfrequency

Check Out the Following Examples:Check Out the Following Examples:

Since the speed of light is constant, Since the speed of light is constant, wavelength & frequency have a constant wavelength & frequency have a constant relationshiprelationship

They are They are inverselyinversely proportional proportional

As wavelength of light decreases, the As wavelength of light decreases, the frequency of light frequency of light increasesincreases

As wavelength of light increases, the As wavelength of light increases, the frequency of light frequency of light decreasesdecreases

How are Energy & Frequency Related?How are Energy & Frequency Related?

They are They are directlydirectly proportional proportional

As frequency increases, energy As frequency increases, energy increasesincreases

As frequency decreases, energy As frequency decreases, energy decreasesdecreases

The Photoelectric EffectThe Photoelectric Effect

Emission of Emission of electronselectrons from a metal when from a metal when light shines on the metallight shines on the metal

Wave TheoryWave Theory says that light of any says that light of any frequency should be capable of frequency should be capable of supplying supplying enough energy to loosen an enough energy to loosen an electronelectron

THIS WAS NOT THE CASETHIS WAS NOT THE CASE There was a minimum frequency that had to There was a minimum frequency that had to

be met before the photoelectric effect be met before the photoelectric effect would occurwould occur

Albert EinsteinAlbert Einstein

1905 – 1905 – “Electromagnetic Radiation“Electromagnetic Radiation has a has a dual wave – particle existence”dual wave – particle existence”

A particle of electromagnetic radiation A particle of electromagnetic radiation (light) with zero mass and a quantum (light) with zero mass and a quantum of energy is called a of energy is called a photonphoton

HypothesisHypothesis::

Light could be a waveLight could be a wave Light could be a stream of particlesLight could be a stream of particles Photon =Photon = particle of radiationparticle of radiation

has no masshas no mass

carries a quantum of carries a quantum of energyenergy

E E photonphoton = (h) x (v)= (h) x (v)

This won Einstein his only Nobel PrizeThis won Einstein his only Nobel Prize

Photon = a particle of light.

Electromagnetic Radiation ALL light. Visible AND Invisible

visible light , x-rays, gamma rays, radio waves, microwaves, ultraviolet rays, infrared.

Photon a particle of light

Laser Laser

Can electrons act as a particle and a Can electrons act as a particle and a wave???wave???

French Scientist: French Scientist: Louis de BroglieLouis de Broglie

Discovered that Discovered that electronselectrons have a have a similar amount of energy as a similar amount of energy as a photonphoton

German Physicist Max Planck discovered:German Physicist Max Planck discovered:

Objects emit energy in small, specific Objects emit energy in small, specific amounts called amounts called quantaquanta

Quantum – minimum quantity of energy that Quantum – minimum quantity of energy that can be lost or gained by an electroncan be lost or gained by an electron

(His work proved Einstein correct)(His work proved Einstein correct)

E = h * vE = h * v

E = energyE = energy

h = Planck’s constant (6.626E-34 J*s)h = Planck’s constant (6.626E-34 J*s)

v = frequency of radiationv = frequency of radiation

2020thth Century Century

Atomic Theory:Atomic Theory: Neils Bohr’sNeils Bohr’s theory involved theory involved

absorption and emission of absorption and emission of lightlight

When an electron jumped to a When an electron jumped to a higherhigher energy level, it absorbed energyenergy level, it absorbed energy

When an electron returned to a When an electron returned to a lowerlower energy level it gave off energy in the energy level it gave off energy in the form of form of lightlight

Bohr Model of the AtomBohr Model of the Atom

•When an electron jumps to a higher energy level, it absorbs energy

(green arrows).•When an electron returns

to a lower energy level, it gives off energy in the form of light (purple arrows)

Quantum MechanicsQuantum Mechanics

The energy of the particles in the Bohr atom is

restricted to certain determined values. It can be said that the energy

is quantized; this means that only certain orbits with certain radii exist and any other orbits do not exist.

Quantum MechanicsQuantum MechanicsLet’s see if you can:Let’s see if you can:

Define the EMS (electromagnetic spectrum.

List the various parts of a wave of electromagnetic radiation

Explain how this radiation is “quantized” by the electrons in an atom.

Use this information to determine an unknown element with a flame test.