IB Physics 12 Mr. Jean February 5 th, 2014

The plan: Video clip of the day. Quantum Theory Energy Levels

Some Definitions: Radiation - Electromagnetic Waves (EMR): wave consisting of oscillating electric and magnetic fields that move at the speed of light through space. Quantum: a discrete amount of energy. Quantized: a property of a system that occurs only in multiples of a minimum amount.

Photoelectron: electrons emitted in the photoelectric effect. Photoelectric Effect: the emission of electrons when electromagnetic radiation falls on an object. Incandescent body: object that emits light because of its high temperature.

Quantum Theory Introduction: In the early part of the twentieth century, Einstein's Theory of Relativity and the Quantum Theory shook the world of physics. Einstein's Theory of Relativity was theorized in a year but the Quantum Theory required almost 3 decades to unfold.

Quantum Theory (Modern Physics) By the 1890s, scientists could not explain two troubling phenomena by using traditional Newtonian physics and the wave theory of electromagnetic waves (classical physics).

Black Body Radiation: A blackbody is a "perfect radiator" - it will emit a complete spectrum of electromagnetic radiation. Objects that normally give off no radiation (appear black) can be made to do so by heating them. As the energy added to them increased, the type of radiation emitted changed. –However, at a certain temperature and frequency (ultraviolet range) the graph and experimental data did not continue to produce the expected results.

Black Body Radiation: DfhUhttp:// DfhU

Demonstration (CH-9) Demonstration 9.1 –Physics Folder

Kirchhoff needed a mathematical relationship. He could not determine the relationship so he challenged other scientists to come up with one. It was very complex. When physicists applied classical physics theories, the graph obtained was not what was happening experimentally.

In 1900, Max Planck, did mathematically calculate the observed spectrum of radiation ONLY if he assumed that the vibrations of atoms could only have specific frequencies. According to Planck, the energy given off by atoms was E = nhf where –n: an integer; 0, 1, 2.. –f: frequency of vibration of atom –h: mathematical constant –h: Planck's constant = 6.63x J/Hz or J ・ s energy could only be specific values like hf, 2hf, 3hf, etc.

Check out this website: Black Body Spectrum kbody-spectrumhttp://phet.colorado.edu/en/simulation/blac kbody-spectrum s/the-atom-and-quantum- physics/blackbody-radiation/ s/the-atom-and-quantum- physics/blackbody-radiation/

Planck’s Atoms E = nhf –n: an integer; 0, 1, 2.. –f: frequency of vibration of atom –h: mathematical constant –h: Planck's constant = 6.63x J/Hz or J ・ s

What Planck was essentially saying was that energy emitted or absorbed by atoms is QUANTIZED or exists in packages (bundles) of energy in specific sizes.

BBC – Clash of the Titans 17 – 40 minutes –History an experiments which were the origin of Quantum Theory

Photo Electric Effect:

XSmkhttp:// XSmk