Quantum Physics ….and you thought I couldn’t use Powerpoint
BlackBody Radiation • ALL objects radiate thermal energy based on the vibration of the atoms within the molecules • Cold in the IR range – not visible • Turn up the heat & radiation becomes visible • ROYGBIV (red hot toaster or stove burner, white light bulb filament) • Big l to Short l or • Low f to high f
Planck-Thermodynamics • Says we get the graphs because atomic oscillators’ are only able to oscillate at distinct frequencies: E=nhf Compare to a box being pushed up an incline or lifted up individual steps. In the first case the GPE increases continuously in the second in increments. • The oscillators produce the em wave.
Photoelectric Effect Problem: Wave versus Particle • Any f should remove electrons . Not Observed. • Intensity Energy Regardless of f • Emitted e- energy should depend on Intensity of light beam. Not Observed. • Emitted energy depends on f • Waves of light spread energy across metal. Requires time for e- to absorb energy and fly off. Not Observed.
Light & Einstein Light is a PARTICLE • Einstein: light has no mass, but DOES have KE • Einstein predicted light waves have p! • Had no way of confirming these formulas
Ephoton=hf KEmax=KEelectronf=work function Stopping Voltage used to find Kemax: Ue=KEmax KEmax=hf-f
Photoelectric Effect Graph • y=mx+b • Threshold Frequency = x-intercept • Work Function = y-intercept • Planck’s Constant = slope