1. Light Waves and Particle Characteristics

2. Parts of a Wave = wavelength (lambda) =frequency(nu)

3. Wave Wavelength (m) – Longer wavelengths have lower energy than shorter wavelengths. We say that is inversely proportional to E  1/E Frequency (1/sec) – As the wavelength decreases, the frequency increases We say that is inversely proportional to 

4. Waves We can use the relationship c= to solve for either the wavelength or frequency, when the other is known. C = speed of light – This is constant in a vacuum 3.00 x 10 8 m/sec

5. Example #1 Calculate the wavelength of yellow light emitted by a sodium vapor lamp if the frequency of the radiation is 5.10 x 10 14 Hz? (Hz = 1/sec) C = 3.00 x 10 8 m/s = (5.10 x 10 14 Hz) 5.88 x 10 -7 m =

6. Example #2 What is the wavelength of radiation with a frequency of 1.50 x 10 13 Hz? Does it have a longer or shorter wavelength than red light? c = 3.00 x 10 8 m/s = (1.50 x 10 13 Hz) 2.00 x 10 -5 m = It has a longer wavelength than red light

7. Light Each element has a specific Atomic Emission Spectrum – as specific frequencies of light are emitted What causes the frequencies of light?

8. Light As e- gain Energy, they move to higher energy levels, away from the nucleus They are moving from a Ground State to an Excited State As the e- move back down to Ground State – that Energy must be released

9. Light The amount of Energy that is absorbed or released is known as a Quantum of Energy Energy is proportional to E  hh ww here h = Plank’s Constant

10. Light Plank’s Constant = 6.6262 x 10 -34 Jsec J = Joule (a unit of energy) E ( ) = h (J sec) (1/sec) E (J)

11. Light The greater the jump, the greater the amount of energy that will be released n=6 n=1 released more energy than an e- which moves from n=6 n=5

12. Example #3 How much energy is released by an e- dropping from n=4 n=2 if the light that is emitted has a frequency of 5.55 x 10 14 1/sec? E = h E= 6.6262 x 10 -34 Jsec (5.55 x 10 14 1/sec) E = 3.68 x 10 -19 J

13. Example #4 If an electron releases 4.56 x 10 -19 J of energy as it drops from n=5 n=2, what color of light would be observed?

14. Example 4 continued Begin with E=h 4.56 x 10 -19 J = 6.6262 x 10 -34 Jsec ( ) 6.88 x 10 14 1/sec = Next use c = 3.00 x 10 8 m/sec = (6.88 x 10 14 1/sec) 4.37 x 10 -7 m = Blue light is observed