The Spectroscope: New Meanings in Light Topic 3 – Space and Exploration

Spectral Lines Isaac Newton passed a beam of light through a prism and produced a spectrum of colors. White light, is made up of ALL colors

Spectroscope A spectroscope is a device that has a narrow slit and a prism. It takes light and passes it through this very narrow slit and through the prism This creates much finer detail.

Experiment Joseph von Fraunhofer used a spectroscope to look at the sun. He noticed HUNDREDS of dark lines in the sun’s spectrum (solar spectrum) These dark lines are called spectral lines

Spectroscopy Spectroscopy is the Science of color Vapors of different elements give off different colors through a spectroscope when heated Mercury, when heated, is blue Sodium, when heated, is yellow

Gustav Kirchoff and Robert Bunsen heated all sorts of chemicals and looked at the vapors through a spectroscope They realized ….. NOT ALL THE COLORS OF THE RAINBOW ARE PRESENT!

Each element has its own FINGERPRINT No two elements are exactly the same It is like a human’s fingerprint. The colors that show up are unique to a certain light source.

Three Types of Spectra 1. Emission or bright line spectrum If you heat a gas at low pressure (vacuum), it produces a spectrum that is only a set of bright lines of certain colors on a black background.

2. Continuous Spectrum If you heat a solid, liquid or gas at high pressure, the resulting spectra contain ALL THE COLORS blending into one another. Like a rainbow in the sky.

3. Absorption or Dark Line Spectrum When white light is passed through a cooler gas, the spectrum is a continuous spectrum with dark gaps between colors The gas that the light passes through absorbs or removes some of the colors in the spectrum

THE COMBINATION This is Hydrogen…. Who can explain this?

Diffraction Gratings Spectroscopes usually use prisms to split the light into a spectrum. To get the best detail in a spectrum, a diffraction grating can be used instead of a prism.

This happens because the waves bend around corners and diffract (bend) When light is passed through VERY small openings, a spectrum is produced. This happens because the waves bend around corners and diffract (bend) A device with thousands of closely spaced slits is called a diffraction grating Examples of where diffraction gratings are used: CD’s Holographic trading cards

different sources of light produce different types of these spectra. Also, you know that Kirchoff and Bunsen discovered that each element (when heated in a vacuum) produces a unique pattern of spectral lines.

Solar Spectrum A light that passes through a gas will have spectral lines (dark) where the gas has absorbed the light. The solar spectrum had HUNDREDS of dark lines which means the light had to have passed through several gases in the sun’s atmosphere before reaching Earth

Spectral Analysis By looking at each of these dark lines in the solar spectrum, we can determine which elements are present in the Sun’s atmosphere. COOL!!

Example Hydrogen Helium Sodium Star 1 Star 2