Isaac Newton 1643 - 1727. From Physics class: F g = 9.8 N / kg (mass 2 ) 9.8 N / kg = Gm 1 / r 2 N =...
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Transcript of Isaac Newton 1643 - 1727. From Physics class: F g = 9.8 N / kg (mass 2 ) 9.8 N / kg = Gm 1 / r 2 N =...
Isaac Newton 1643 - 1727
From Physics class:
Fg = 9.8 N / kg (mass2)
9.8 N / kg = Gm1 / r2
N = m / s2 * kg
G = 6.67 x 10-11 Nm2/kg2
•Light behaves like small particles - corpuscles
•Light travels in straight lines
•Reflect off opaque surfaces
•Penetrate transparent materials
White light made of colors
Newton
Problems with Reflecting Telescopes
* Longer focal length harder to make
* Chromatic Aberration
Newtonian Telescope
• Light behaves like waves
– 1600s Christian Huygens • Refraction & Reflection explained by
wave theory of light• Problem – can’t see around corners
By 1800
Light has component parts
Light behaves as a particle
William Herschel 1738 – 1822 – Discovers Infra-red
• 1801 • Johann Wilhelm
Ritter discovers Ultraviolet Light
– 1827 Thomas Young and Augustin Fresnel• Measures wavelength
• Observes interference of waves
http://micro.magnet.fsu.edu/primer/java/interference/doubleslit/
• 1820 Hans Christian Ørsted – Discovers relationship between electricity &
magnetism– In 1802 Italian Gian Domenico Romagnosi had
already announced this was ignored
• 1845 Michael Faraday– Fields
Electric Fields
Magnetic Fields
• Michael Faraday
Light affected by a magnetic field
• 1873 James Clerk Maxwell– finds the mathematical
relationship between electric fields and magnetic fields
Electromagnetic Waves
1. Visible light is EM energy
2. There should be other EM frequencies
• 1889 Heinrich Hertz – Produces small electromagnetic waves that
have properties of light– Produces Radio Waves or “Hertzian waves”
• 1895 Wilhelm Roentgen– Discovers X - Rays
By 1900
Light, Radio and X-rays are Electromagnetic Waves
• 1914 Gamma Rays Included – Henri Becquerel “Becquerel’s Rays”
Radioactivity– Marie & Pierre Curie discover new elements
Polonium & Radium– Paul Villard finds stronger rays emitted by
radium– 1914 Ernest Rutherford measures wavelength
• 1930 Microwaves Explored– WW II pushes research– Commercial Research after war
Early 1900sWe know “light” is a form of electromagnetic radiation
There are many different “kinds” of light or electromagnetic radiation
Atmospheric Window
Think of Light as a stream of particles
Each particle has a certain amount of energy
Is Light a Wave or a Particle?
Wave Particle Duality