Photon Model of Photon Model of Light & Line Light & Line

SpectraSpectra

Atomic SpectraAtomic Spectra

Most sources of radiant energy (ex. light bulbs) produce many different wavelengths of light (continuous spectrum).

Elements produce certain colors when excited (via electrical discharge or heat).

H Ne

Spectral lines can determine the chemical composition of various materials or objects (ex. stars).

Spectral lines can also tell us about star movement!!!

YES CHILDREN………STARS DO MOVE!!!

Moving towards equipment

Moving away from equipment

n = 1

n = 2

n = 3

Laser

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Energy is absorbed by the nucleus, then transferred to an e-, causing it to move to a higher energy level.

What does the atomic spectrum of an element tell us?

Photon Model of LightPhoton Model of Light

What does the atomic spectrum of an element tell us?

Electrons (e-) are either emitting or absorbing energy by changing energy states. Energy lost is in the form of a photon. Each element emits a distinct amount of energy

n = 1

n = 2

n = 3

n = principal quantum #

# = Energy

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Photon Model of LightPhoton Model of Light

Photon Model of LightPhoton Model of Light

This phenomena couldn’t be explained by the wave This phenomena couldn’t be explained by the wave model of light. model of light.

1921- Albert Einstein proposed photon model of 1921- Albert Einstein proposed photon model of light using the Plank’s energy equation:light using the Plank’s energy equation:

E = hE = hffh = Plank’s Constant = 6.63 x 10h = Plank’s Constant = 6.63 x 10-34-34 J•s J•s

1 eV = 1.6 x 101 eV = 1.6 x 10-19-19JJ

Sample ProblemEach Photon of yellow light, the predominant color in sunlight, carries an energy of 2.5 eV. What is the frequency of this light?

E = hE = hff

h = 6.63 x 10h = 6.63 x 10-34-34 J•s J•s

1 eV = 1.6 x 101 eV = 1.6 x 10-19-19JJf = f = E/hE/h

f = f = (2.5 (2.5 eVeV) () (1.6 x 101.6 x 10-19-19J/eVJ/eV)) / 6.63 x 10/ 6.63 x 10-34-34

J•sJ•sf = f = 6.0 x 106.0 x 101414 Hz Hz

Sometimes when certain Sometimes when certain f f of light shine on of light shine on surfaces, it can cause e- to eject from the materials surfaces, it can cause e- to eject from the materials surface.surface.

Photoelectric EffectPhotoelectric Effect

Photon Model of LightPhoton Model of Light

Umm……ok and where do we use this stuff???Umm……ok and where do we use this stuff???

Photon Model of LightPhoton Model of Light