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

Kirchoff-Bunsen Experiment ~ 1855

The Sun’s Spectrum The sun has more than 30k dark lines

Iron in the Sun

The Rosette Nebula The NGC 2363 Nebula Horsehead Nebula The reddish color seen in these pictures comes from an emission line from hydrogen

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 c = f

Since light is a wave it must have a wavelength, denoted by. Colors and Wavelengths

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.

Blackbody 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

Hydrogen

The Helium Atom

The Origin of the Spectral Lines

Creation of Red and Blue Light

Ground State and Excited State

Lyman, Balmer and Paschen Series of Lines

Balmer Lines in a Spectrum of a Star

The Doppler Effect

Rotating and Revolving Planets

Star Cluster NGC 3293 in Carina T = ? UV? Visible?