Physics 7C SS1, Lecture 10 Quiz 4 Quantum Mechanics Evaluations

Agenda Any questions about electric potential energy (PE elec ), electric potential (V), their relationships to F elec and/or E? Any questions about magnetism? Quiz 4 Final information Quantum Mechanics Evaluations

Quiz 4 Current flows into the page; asked about field and force at star’s location

Final Exam As comprehensive as 1hr 15 minutes can be Bring calculator, straight edge, ID As comprehensive as 1hr 15 minutes can be Probably 5 questions (?)

Quantum Mechanics Light and matter both behave like waves sometimes and like particles other times Confining waves to an area leads to standing wave patterns For bound matter, this results in only certain available energy levels Bound matter can gain or lose energy only between the available levels To conserve energy, usually a photon is absorbed or emitted with the correct energy (frequency)

Experimental Evidence: Photons Electrons in metal: Free to move Bound to metal Think of as binding energy Goal: free from metal Shine light to add energy. How can we get high energy light?! Laser Metal v

Energy: Photon Model Changing color of light: If red light does not free electrons, sometimes other colors will If purple light does not free electrons, no visible light will. Color (frequency) of light is related to the energy! E = hf = energy of one photon h: Plank’s Constant =  Js Increasing intensity corresponds to increasing number of photons.

Which type of EM radiation is highest energy? b) Visible c) X-ray a) Radio

Quantum Mechanics: Light As a wave As a particle: E=hf Matter As a wave: =h/p As a particle: as you have always studied!

Quantum Mechanics Consequences of wave nature of matter 2-slit interference occurs for particles Confining a particle leads to standing waves Different standing waves have different wavelengths Different wavelengths correspond to different momenta Different momenta correspond to different energies All these things are quantized: only certain values are allowed

Atoms: electrons bound to nucleus Molecules: can model bonds as springs, with atoms bound together Examples of bound particles N N

Example of energy levels: Emission Spectra Add energy to an element and wait. Each element emits light of certain colors. Why? Hydrogen Helium Iron

Emission Spectra Each of the three marked transitions correspond to visible light. Which one is responsible for the red photon? E1E1 E2E2 E3E3 E4E4 E5E5 a b c

The three previous transitions corresponded to visible light. What part of the spectrum might the bold arrow correspond to? a)Green light b)Infrared (IR) c)Ultraviolet d)Microwave e)Gamma ray Emission Spectra E1E1 E2E2 E3E3 E4E4 E5E5

The End Questions? You’re 1DL and 1 final exam away from completing physics. Congrats! Course Evaluations