Lecture 4 Wavelength Amplitude Frequency (speed of light) = λv (wave number) as wavelength ↑, frequency ↓ wave with labels for wavelength, amplitude, and frequency 10⁻¹⁵ 10⁻¹⁴ 10⁻¹³ 10⁻¹² 10⁻¹¹ 10⁻¹⁰ 10⁻⁹ 10⁻⁸ 10⁻⁷ 10⁻⁶ 10⁻⁵ 10⁻⁴ 10⁻³ 10⁻² 10⁻¹ 10⁰ 10¹ 10² γ-rays x-rays UV visible IR (infrared) micro radio which of the following are examples of electromagnetic radiation? a) radio waves, b) microwaves, c) cosmic waves, d) beta decay a) b as the wavelength of light increases... a) ↑ v, ↑ amplitude, b) ↑ v, ↓ amplitude, c) ↑ period, d) ↓ v c) ↑ period, ↓ v in-phase / constructive bright two waves in phase out-of-phase / destructive dark two waves out of phase photoelectric effect diagram showing the photoelectric effect below threshold v, no current is generated despite intensity (amp) above it, e- are ejected (current) if you try to determine e- position, light affects momentum photons have E and momentum but 0 mass E = hν = h(c/λ) = KE h = planck's constant = 6.626 x 10⁻³⁴ J-s graph showing the kinetic energy of ejected electrons as a function of the frequency of incident light energy is quantized as photons. E is of one photon hν = E = KE + Φ, Φ = work function total E + KE (surplus) after reaching Φ Φ (eV): cost to get out v threshold ↑ intensity! a certain amount amp increase of E (v) needed amount of e- is kick ball w/o it rolling back ejected ↑ current (e-/sec) but not e- one photon → one e- ejected