The Nature of Light

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Transcript The Nature of Light

The Nature of Light
A Prism “Breaks Up” White Light
When white light passes through a prism a spectrum is formed.
Adding a Second Prism
Three Types of Spectrums
Three Types of Spectrums
Kirchoff-Bunsen Experiment ~ 1855
The Sun’s
The sun has
more than 30k
dark lines
Iron in the Sun
The NGC 2363 Nebula
The Rosette Nebula
The reddish color seen
in these pictures comes
from an emission line
from hydrogen
Horsehead Nebula
Young’s Double-Slit Experiment ~ 1801
Electromagnetic Radiation
Light consists of two perpendicular waves.
One wave is an electric field, the other is a magnetic field.
The wave travels at a speed c, which is orthogonal to both waves.
Light Has Wave-Like Properties
 = Wavelength,
measure in meters
 = Period, measured in sec/cycle
f = Frequency, measured in cycles/sec
 = 1/ f
Colors and Wavelengths
Since light is a wave it must have
a wavelength, denoted by .
Absorption & Emission Lines
Emission Lines for Various Elements
Do lines exist below 400 m and above 700  m?
The Electromagnetic Spectrum
As the wavelength increases the frequency decreases.
Gamma rays have
the shortest
Radio waves have
the longest
Radiation and the Earth’s Atmosphere
High f waves do not make it to the surface, some IR and microwaves
are absorbed by water. Low f radio waves are blocked by the Earth’s
ionosphere. They all must be observed from space.
Radiation Curves
Wien’s Shift
Combine the Star’s Spectrum
with it’s Blackbody Curve
How Fast Does Light Travel?
Why is the Sky Blue?
Why is the Setting/Rising Sun Red?
The Rutherford Experiment
-particles are shot at a thin film of gold foil. Most of the particles
pass straight through foil. Some of the particles bounced back.
Bohr Atom
The Helium Atom
The Origin of the Spectral Lines
Creation of Red and Blue Light
Ground State
Excited State
Lyman, Balmer and Paschen Series of Lines
Balmer Lines in a Spectrum of a Star
The Doppler Effect
The Doppler Effect
Rotating and Revolving Planets
Star Cluster NGC 3293 in Carina