1. Lights & Quantum Mechanics Notes

2. Introduction to Light (10 minutes)

3. Light • light energy particles are called photons • photons are quantized • Is more than visible light • All types of light, visible and invisible, are called electromagnetic radiation • has dual properties • wave property • particle property • E = h∙ʋ • h = Planck’s constant = 6.626×10-34J∙sec • ʋ (nu) = frequency = # of waves passing per second

4. Electromagnetic radiation ------------------------ Energy increases ------------------------------------------------------------- ---------------------- Wavelength decreases ---------------------------------------------------------- ---------------------- Frequency increases -------------------------------------------------------------

5. Waves amplitude 1) wavelength = λ (lambda) = width of one full wave 2) frequency = ʋ (nu) = # of waves passing a point in one second, expressed in Hz (hertz = sec-1) or cycles per second 3) velocity ≈ speed = λ∙ʋ (λ and ʋ are inversely proportional) speed of light (of all types) = c = 2.998×108 m/sec 4) E = h∙ ʋ (E and ʋ are directly proportional)

6. Example • Calculate the wavelength (λ) of the light that has the frequency (ʋ) of 5.10×1014 Hz. The speed of light (c) is 2.998×108 m/sec. (Sol) c = λ∙ʋ 2.998×108 m/sec = λ∙ (5.10×1014 sec-1)

7. E, λ and ʋ • E = h∙ʋ • Energy (E) and frequency (ʋ) are directly proportional • E = h·c/λ • Energy (E) and wavelength (λ) are inversely proportional

8. Electrons Quantized * Proved by photoelectric effect

9. Emission Spectra Energy given off when electrons move to lower energy states are shown as spectral lines • ground state: electrons are in • their natural state • excited state: electrons are in • higher energy state after • absorbing energy

10. Example: hydrogen spectra

11. Quantum vs. Classical • Quantum mechanics • deals with very small particles such as atoms, electrons, and photons • based on wave properties of particles and Heisenberg uncertainty principle • Heisenberg uncertainty principle: never know both the velocity and the position of a particle at the same time • Classical mechanics • deals with large objects • accurately predicts the velocity and the position of an object