Objective: I will relate the electromagnetic spectrum to wavelengths of light energy. 9/30/14

ELECTROMAGNETIC SPECTRUM  All energy travels in waves  Light, which is energy, travels in waves  The electromagnetic spectrum shows us all of the different wavelengths of light that are emitted (given off) by objects  Wavelength is the distance from crest to crest of a wave

ELECTROMAGNETIC SPECTRUM

VISIBLE LIGHT  The visible light spectrum is only a small portion of the Electromagnetic Spectrum  The visible light spectrum is the portion of the EMS we can see [ nanometers (nm)] ROY G. BIV

VISIBLE LIGHT  Visible light comes from two sources: luminous (gives off its own light) and illuminated (reflects light) objects  WITHOUT LIGHT, THERE WOULD BE NO SIGHT!  When looking at an illuminated object, we see the color reflected back at us (ex. A red shirt is reflecting the wavelength of red).  White reflects all colors, black absorbs all colors

DIFFRACTION GRATING  A diffraction grating separates white light coming from an object into the colors of the visible spectrum  A spectrograph is used to measure light  It contains a diffraction grating along with a camera to record incoming observations

SPECTROSCOPY  Spectroscopy- the study of light coming from objects in space  Each element gives off its own unique spectrum of light.

SPECTROSCOPY  Spectroscopy can be used to measure what elements are in an object giving off light, such as stars and galaxies  It can also be used to measure the temperature, density, and mass (among other things) of the distant object

OTHER FORMS OF LIGHT  Astronomers use many different types of telescopes to study electromagnetic energy  Radio telescopes are used for objects very far away because they measure very long wavelengths that are able to travel through objects  Microwave telescopes were used to map the early Universe (COBE & WMAP)