Historical development of light theory
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Transcript of Historical development of light theory
Development of Light Theory
Historical Milestones
Historical Development
Isaac Newton – Particle Theory & PrismChristiaan Huygens – Wave TheoryThomas Young – Double-Slit Experiment James Maxwell – Electromagnetic TheoryHeinrich Hertz – Radiowaves & Wireless
ExperimentWilliam Roentgen – X-raysMax Planck – Radiation TheoryAlbert Einstein – Photo Model
Isaac Newton (1642-1727)
Particle Model of Light (1671)
Light rays is comprised of a stream of massless particles
Particle Model of Light (1671)
Explains straight-line propagation of light: Follows laws of reflection and refraction
Explains colours of light: White light contains different colour particles Prism sorts the different particles of light
http://www.sciencephoto.com/image/227396/530wm/H4140126-Newton_s_optics-SPL.jpg
Christiaan Huygens (1629-1695)
Wave Theory (1678)
Light is a wave that can transfer energy without transferring matter
Light waves have varying wavelengths, frequencies, speeds and amplitude
Wave Theory (1678)
Follows laws of reflection and refraction Explains diffraction: the effect of waves
when encountering an obstacle Constructive and destructive interference
http://www.sciencephoto.com/image/2511/530wm/A1800254-Water_waves-SPL.jpg
Wave Theory Waves are additive:
constructive interference Example: waves in the ocean
are bigger when more than one wave moves together
Waves are subtractive: destructive interference A wave that meets a trough
of equal amplitude cancel each other out (net zero amplitude)
http://upload.wikimedia.org/wikipedia/commons/3/33/Doubleslit3Dspectrum.gif http://en.wikipedia.org/wiki/File:Doubleslit.svg
Thomas Young (1773 – 1829)
Wave Theory of Light Proved that light
propagates as a wave Performed an
experiment that demonstrated interference patterns in light that followed the rules of diffraction seen in water waves
http://www.thestargarden.co.uk/images/163.%20Double%20slit%20waves.png
A coherent light is shone through a thin plate pierced by two parallel slits
Double-Slit Experiment (1801) wave nature of light causes the light waves
passing through the two slits to interfere, producing bright and dark bands on the screen
James Maxwell (1831–1879)
Electromagnetic Theory Proposed that electric
and magnetic fields travel through space in the form of waves at the speed of light.
Electricity, magnetism and light all manifest together in the form of an electromagnetic field that does not require a medium for transmission.
Heinrich Hertz (1857-1894)
Discovered radio waves
First to prove the existence of electromagnetic waves by using a device that transmit and receive radio pulses
Hertz Wireless Experiment (1887)
http://www.sparkmuseum.com/HERTZ.HTM
Hertz Wireless Experiment (1887)
Engineered a device that makes a spark
If the spark sent EM waves, it would be transmitted and picked up by the receiver which would also spark
Also measured length and velocity of EM wave
Showed that EM wave reflected and refracted the same as light waves
Proved that light is electromagnetic radiation
William Konrad Roentgen (1845-1923)
Produced and detected x-rays
Nobel Prize in Physics (1901)
Max Planck (1858-1947) Radiation theory:
electromagnetic radiation is emitted in quanta
Light energy is not continuous like in a wave
Rather light is delivered in small parcels / packets of energy
Albert Einstein (1879-1955)
Photon model Light functions both
as particle and wave Light is composed of
particles (photons) that travel as waves
Each photon has energy that is proportional to the frequency of its wave