Electron BehaviorElectron Behavior

Electron absorb energy and jump to higher Electron absorb energy and jump to higher energy level energy level (Excited State).(Excited State).

Immediately fall back to original level Immediately fall back to original level (Ground State)(Ground State) emitting the energy in the emitting the energy in the form of electromagnetic radiation.form of electromagnetic radiation.

Energy is released in discrete packets Energy is released in discrete packets called called quantaquanta..

The process is referred to as a “quantum The process is referred to as a “quantum leap.”leap.”

Light and Atomic SpectraLight and Atomic Spectra

Every element emits light when its excited.Every element emits light when its excited.Light quanta are called photons.Light quanta are called photons.Atomic Emission Spectra the light emitted Atomic Emission Spectra the light emitted

by an electron and passed through a by an electron and passed through a prism. Consists of a few lines are called prism. Consists of a few lines are called line spectra.line spectra.

The emission spectrum of each element is The emission spectrum of each element is unique to that element.unique to that element.

Energy Absorption and Energy Absorption and EmissionEmission

Photoelectric EffectPhotoelectric Effect

Albert Einstein proposed that light could be Albert Einstein proposed that light could be described as quanta of energy that behaves described as quanta of energy that behaves like particles.like particles.

Photoelectric effect – metals eject electrons Photoelectric effect – metals eject electrons when light shines on them.when light shines on them.

Only when the frequency of light is above the Only when the frequency of light is above the threshold frequency will the photoelectric threshold frequency will the photoelectric effect occur.effect occur.

Practical use: solar panels, solar calculatorsPractical use: solar panels, solar calculators

Electromagnetic SpectrumElectromagnetic Spectrum

Electromagnetic Spectrum

Radio WavesMicrowavesInfrared WavesVisible Light WavesUltraviolet WavesX-raysGamma Rays

Longest Wavelength/Lowest Frequency

Shortest Wavelength/Highest Frequency

Visible Light Spectrum

Memory device: ROY G. BIV red-orange-yellow-green-blue-

indigo-violet Orders colors from lowest

frequency/longest wavelength to highest frequency/shortest wavelength.

Anatomy of a WaveAnatomy of a WaveWavelength (Wavelength (λλ):):

Distance between Distance between analogous parts of a analogous parts of a wave.wave.

Crest:Crest: Top of wave Top of waveTroughTrough:: Bottom of Bottom of

wavewaveAmplitudeAmplitude:: Height of Height of

wave (related to wave (related to amount of energy a amount of energy a wave has)wave has)

Resting Position

FrequencyFrequencyFrequency (Frequency (f)f):: the number of wave cycles the number of wave cycles

that pass in a given amount of time.that pass in a given amount of time. If the time is 1 second the unit for frequency If the time is 1 second the unit for frequency

is is HertzHertz (Hz, (Hz, 11//ss, s, s-1-1).).

Frequency vs. WavelengthFrequency vs. WavelengthFrequency and wavelength have an

inverse relationship.As frequency increases, the wavelength

decreases..As frequency decreases, the wavelength As frequency decreases, the wavelength

increases.increases.

EquationsEquationsWave Velocity/SpeedWave Velocity/SpeedThis formula measures the velocity/speed This formula measures the velocity/speed

of a wave.of a wave.

v = f x v = f x λλv = velocityv = velocity f = frequencyf = frequencyλλ = wavelength = wavelengthSpeed of light in a vacuum =Speed of light in a vacuum =

3.0 x 103.0 x 101010 cm/s or cm/s or 3.0 x 103.0 x 1088 m/s m/s

PracticePractice1.1. A wave is traveling at a velocity of 12 m/s and A wave is traveling at a velocity of 12 m/s and

its wavelength is 3m. Calculate wave its wavelength is 3m. Calculate wave frequency.frequency.

2.2. Calculate the wavelength of yellow light Calculate the wavelength of yellow light emitted by a sodium lamp if the frequency of emitted by a sodium lamp if the frequency of the radiation is 5.10 x 10the radiation is 5.10 x 101414 Hz (5.1 x 10 Hz (5.1 x 101414 s s-1-1). ). The speed of all light in a vacuum is 3.0 x 10The speed of all light in a vacuum is 3.0 x 101010 cm/s.cm/s.

3.3. What frequency is radiation with a wavelength What frequency is radiation with a wavelength of 5.00 x 10of 5.00 x 10-6-6 cm? The speed of all light in a cm? The speed of all light in a vacuum is 3.0 x 10vacuum is 3.0 x 101010 cm/s. In what region of cm/s. In what region of the EM Spectrum is this radiation. the EM Spectrum is this radiation.

EquationsEquationsPlanck’s ConstantPlanck’s ConstantThis formula measures energy of a This formula measures energy of a

quantum. quantum.

E = h x fE = h x fh = 6.6262 x 10h = 6.6262 x 10-34-34 J • s J • s f = frequencyf = frequencyEE = amount of radiant energy absorbed or = amount of radiant energy absorbed or

emitted.emitted.

PracticePractice1.1. Orange light has a frequency of 4.8x10Orange light has a frequency of 4.8x1014 14

ss -1 -1. What is the energy of one quantum of . What is the energy of one quantum of orange light?orange light?

2.2. The threshold photoelectric effect in The threshold photoelectric effect in tungsten is produced by light of tungsten is produced by light of wavelength 2.6 x 10wavelength 2.6 x 10-7-7 m. Give the energy m. Give the energy of a photon of this light in joules (speed of of a photon of this light in joules (speed of light is light is 3.0 x 103.0 x 1088 m/s). m/s).