Electromagnetic Radiation

The transfer of energy by electromagnetic waves. The speed of an electromagnetic wave is a product of its wavelength and frequency. c = λƒ (λ) Wavelength The distance between two successive wave crests. (ƒ) Frequency The number of waves that pass a given point per second. c = the speed of electromagnetic wave (light) in a vacuum

Speed of Light c = 300,000,000 m/s c = 300,000 km/s c = 186, 000 miles/s Fastest Probe: 45 km/s or 100,000 miles/hour Satellite: 17,000 miles/hour

Speed of Light Planets & GalaxiesDestination Distance from Earth (light-years) Time at Light Speed Moon seconds Sun minutes Mercury minutes Venus minutes Mars minutes Jupiter minutes Saturn hours Uranus hours Neptune hours Pluto hours Alpha Centauri years Sirius (Dog star) years Arcturus3636 years Pleiades Cluster years Betelgeuse years Deneb1,6001,600 years Crab Nebula4,0004,000 years Center of Milky Way38,00038,000 years Magellanic Clouds150,000150,000 years Andromeda Galaxy2,200,0002,200,000 years

Speed of Light Solar System Travel SpeedTime to JupiterTime to SaturnTime to Cen Freeway Speed75 mph600 yrs1200 yrs38 million yrs Jetliner Speed500 mph90 yrs180 yrs6 million yrs Concorde Speed (Mach 2) 1350 mph33 yrs66 yrs2 million yrs Spacecraft Speed (Voyager) 40,000 mph1.5 yrs3 yrs70,000 * yrs

Electromagnetic Spectrum Electromagnetic spectrum All types of electromagnetic radiation arranged according to wavelength and frequency.

Comparing Electromagnetic Radiation Red light has a longer wavelength than blue light Blue light has a greater frequency than red light Greater frequency  more energy More energy  higher temperature Blue stars are hotter than red stars

The surface temperature of a star determines its color Cool  Hot Red Orange Yellow White Blue

Color & Temperature

What color is the Sun?

From space our sun looks like this WHITE (at best a very pale yellow)

There are three types of spectra: continuous, emission, and absorption

Absorption Line Spectrum (dark lines) Used to determines a star’s composition Elements in a star absorb specific wavelengths of light. The spectrum produced by a light source passing through a gas contains DARK lines at certain wavelengths because each element present in the gas ABSORBS specific wavelengths of light.

Continuous Spectrum (no lines) Has no breaks in its spectra. When light from an ordinary bulb is shined through a prism or a glowing solid, liquid or compressed gas. Emission Line Spectrum (bright lines) The spectrum produced by a non-compressed gas contains BRIGHT lines at certain wavelengths Each element in a gas EMITS specific wavelengths of light.

Identifying Elements in Stars A spectrum produced by a star is an absorption line spectrum. The pattern of the dark absorption lines of an element is exactly the same as the bright emission lines for that same element. By comparing laboratory emission line spectra of different gases with the absorption line spectrum of a star, the composition of the star can be determined.

Doppler Shift A shift in wavelength of a spectrum lines

Doppler Shift Blue shift Wavelength decreases to the blue side of the spectrum. Occurs when and object is moving closer Red shift Wavelength increases to the red side of the spectrum Occurs when an object is moving further away.

Doppler Shift