2. Particles as waves and Light as particles Chapter 6 part II

3. Energy is Quantized Energy can only occur in discrete units of size hv. Each packet is called a quantum. Energy can only be transferred in whole quanta. Energy seems to have particle like behavior.

4. Photons Einstein proposed that electromagnetic radiation is quantized. These light can be viewed as a stream of particles. Each particle is a photon, with energy of: E photon =hv=hc/

5. Theory of Relativity Einstein went on to propose this: E=mc 2 Energy has mass!!!

6. If E=mc 2 and E=hc/ …Then m = (E/c 2 ) E photon = hc Substitute hc for E Then m= (E/c 2 ) = (hc/ ) = h c 2 c This means that a photon appears to have mass!

7. The dual nature of light Compton working with x-rays and electrons seems to have proved this. Energy is quantized. Electromagnetic radiation once thought to act only as waves, seems to also have the characteristics of particles. Can matter have wave- like characteristics?

8. Louis de Broglie de Broglie solved the problem of the wavelike behavior of a particle. Then m= h (velocity v ) Then solving for we get h m v This is called de Broglie’s equation.

9. For example: Compare the wavelength of an electron (m=9.11x10 -31 kg) traveling at a speed of 1.0x10 7 m/s with that of a baseball (m=0.10kg) traveling at 35 m/s

10. Answer: =h/ m v h= 6.626 x 10 -34 Js 1 J= 1kg m 2 /s 2 For electron = 6.626 x 10 -34 (kgmm)/s (9.11x10 -31 kg)(1.0x10 7 m/s) Answer: 7.27 x 10 -11 m

11. And the Ball?? 1.9x10 -34 m

12. Atomic Spectrum of Hydrogen When light is passed through a prism one gets an emission spectrum. When all wavelengths are possible one gets a continuous spectrum. When energy is quantized the spectrum is a line spectrum, or discrete.

13. Light & Electromagnetic Radiation The light spectrum is continuous. All the wavelengths of light may pass.

14. The hydrogen emission spectrum: Is discrete. This indicates only certain energies are allowed for the electron in the hydrogen atom.

15. Hydrogen is discrete as the energy of electrons are quantized. ∆E =hv= hc/ is the wavelength of light emitted. Since the line is discrete on certain energies are possible for the hydrogen electron.

16. The Bohr model: Bohr’s quantum model proposed that electrons in a hydrogen atom move around the nucleus in certain allowed circular orbits.

19. Bohr’s equation Z is the nuclear charge n is an integer representing the orbital, larger n= larger radius n=1 is the ground state