Nature of light and atomic spectrum

Energy from the sun Fusion – process of 2

nuclei that combine to make one (a new element ) and emitting large amounts of energy.

The sun is a giant ball of hydrogen gas undergoing a fusion reaction – releasing energy.

We know that energy as electromagnetic radiation

Electromagnetic Spectrum

Seeing color White light contains all

visible light spectrum R O Y G B V We see….

Black – absorbing all colors White – reflecting all colors Color – ex: red – reflecting

red and absorbing all other colors

White Light

Example – sun lightPasses through prism & separates into continuous spectrum.

Called continuous because all portions are visible – no blank areas

How is light formed?

All electrons in an atom exist naturally in their “ground state” e- configuration (all want to be close to nucleus – lower in energy)

If energy is added – electrons move to higher energy level – “excited state” – but don’t stay.

Electrons fall back to ground state and release light

How is light formed?An electron will jump to a higher

energy level by absorbing energy.

An electron will fall back to ground state by releasing light

http://www.colorado.edu/physics/2000/quantumzone/bohr.html

Atomic Emission SpectraElement’s atomic emission spectra is unique - used to determine an unknown compound.

Like a fingerprintAll elements have a different atomic emission spectrum

Found by using a spectroscope.

What is a spectroscope?Instrument designed to visually

observe spectra by splitting the LIGHT into its components.

Usually has PRISM or a DIFFRACTION GRATING to split light into components.

Diffraction gratings consist usually of thousands of narrow, closely spaced parallel slits (or grooves).

White light passed through a prism

One color of light passed through a prism

Continuous Spectrum

Emission Spectrum

Absorption Spectrum

continuous

emission

absorption

Hydrogen spectrum

Helium spectrum

The light of the gas is split into its components or an emission

spectrum