Electromagnetic Energy in Light and Plant Development | NRSC 683, Study notes of Earth Sciences

Download Electromagnetic Energy in Light and Plant Development | NRSC 683 and more Study notes Earth Sciences in PDF only on Docsity! NRSC 683 Light and Plant Development Spring 2005 Lecture 2 II. Electromagnetic Energy Velocity of Light Galileo (1564-1642) First attempts to measure Ole Römer (1676-1710) Occlusion of moons of Jupiter Albert Michelson (1852-1931) Rotating octagonal mirror 2.997923 x 108 m s-1 Nobel Prize 1907 - 1st American Wave Nature of Light Christian Huygens (1629-1695) Treatise on Light (1673) Interference (Draw) Isaac Newton Corpuscular Theory of Light (1675) Particulate Nature of Light Thomas Young (1773-1829) Experimentally confirmed Huygens' theory (1805) Double slit interference (Draw) Maxwell (1831-1879) Electromagnetic Theory of Light (1873) Light energy transversly propagated in straight lines as a sine wave 2 components (Draw) 1. Electrical Vector 2. Magnetic Vector Transverse propagation always in phase same amplitude Wavelength ( Distance between 2 maxima in m Period () Time to complete one full cycle in s Frequency () Number of oscillations per unit time (Hz or s-1) c =  c/ Frequency inversly proportional to wavelength Related to each other as a function of the velocity of light >  shorter  longer  eg. 300 nm = 3 x 108 m s-1/ 3 x 10-7 m = 1 x 1015 Hz at 600 nm = 3 x 108 m s-1/ 6 x 10-7 m = 5 x 1014 Hz or to calculate wavelength  = c/ for 1 Mhz (radio)  = 3 x 108 m s-1/ 1 x 106 s-1 = 300 m Quantum Theory of Light Max Planck (1900) Dual Nature of Light Discrete Packets of Energy – Photon (Compton 1921) Train of Oscillations E = h  = c /  E = h c /  h = 6.63 x 10-34 J s Energy of a Photon @ 300 nm E = (6.63 x 10 -34 J s) (3 x 108 m s-1) / 3 x 10-7 m E = 6.63 x 10 -19 J or E = 6.63 x 10 -19 J / 1.6 x 10 -19 J V -1 E = 4.14 V @ 600 nm E = (6.63 x 10-34 J s) (3 x 108 m s-1) / 6 x 10-7 m E = 3.31 x 10-19 J or E = 3.31 x 10-19 J / 1.6 x 10-19 J V-1 E = 2.07 V Albert Einstein (1905) Photoelectric Effect (Draw) Experimental confirmation of Planck’s Theory Excitation of electron dependent only on the frequency of light Neils Bohr (1913) Principle of Complimentarity