1. Photon Model of Light & Line Spectra

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

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

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

5. Spectral lines can also tell us about star movement!!! YES CHILDREN………STARS DO MOVE!!! Moving towards equipment Moving away from equipment

6. n = 1 n = 2 n = 3 Laser - 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 Light

7. 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 - - Photon Model of Light

8. This phenomena couldn’t be explained by the wave model of light. 1921- Albert Einstein proposed photon model of light using the Plank’s energy equation: E = hf h = Plank’s Constant = 6.63 x 10 -34 Js 1 eV = 1.6 x 10 -19 J 1 eV = 1.6 x 10 -19 J

9. Sample Problem Each Photon of yellow light, the predominant color in sunlight, carries an energy of 2.5 eV. What is the frequency of this light? E = hf h = 6.63 x 10 -34 Js 1 eV = 1.6 x 10 -19 J 1 eV = 1.6 x 10 -19 J f = E/h f = (2.5 eV ) ( 1.6 x 10 -19 J/eV ) / 6.63 x 10 -34 Js f = 6.0 x 10 14 Hz

10. Sometimes when certain f of light shine on surfaces, it can cause e- to eject from the materials surface. Photoelectric Effect Photon Model of Light

11. Umm……ok and where do we use this stuff??? Photon Model of Light