Electromagnetic Spectrum Review

Frequency Sometimes it is more convenient to talk about light’s frequency Frequency (or f) is the number of wave crests that pass a given point in 1 second (measured in Hertz, Hz) Important relation: fl = c Long wavelenth = low frequency Short wavelength = high frequency

fl = c  Huh?

Properties NO MASS TRAVELS AT THE SPEED OF LIGHT IN A VACUUM MOVES IN BUNDLES OF ENERGY CALLED PHOTONS AS FREQUENCY INCREASES, ENERGY OF PHOTONS INCREASES

Waves Wavelength Crest Wave Height Trough

Wavelength determines type of EM

Light and Color The nanometer (10-9 m) is the convenient unit Red = 700 nm (longest visible wavelength), violet = 400 nm (shortest visible wavelength) Colors to which the human eye is sensitive is referred to as the visible spectrum In the wave theory, color is determined by the light’s wavelength (symbolized as l)

Low Energy High Energy Long wavelength Short wavelength Low frequency High frequency

Rankings Radio Longest Lowest Lowest Microwave Infrared Visible Wavelength Frequency Energy Radio Longest Lowest Lowest Microwave Infrared Visible Ultraviolet X-ray Gamma Ray Cosmic Ray Shortest Highest Highest

Radiation and Temperature As an object’s temperature increases, the object radiates light more strongly at shorter wavelengths. Blue has more energy than red.

Hydrogen spectrum 410 nm 434 nm 486 nm 656 nm Emission spectrum because these are the colors it gives off or emits. Called a line spectrum. There are just a few discrete lines showing 410 nm 434 nm 486 nm 656 nm Hydrogen spectrum

Different elements have different spectra…like fingerprints for elements

The Visible Spectrum

Different types of spectra Continuous spectrum All colors present Emission-line spectrum Produced by hot gases Only certain wavelengths appear Absorption-line spectrum A spectrum with dark lines missing Caused by atoms absorbing certain wavelengths Same wavelengths as found in emission spectra for the same atom

Hydrogen Continuous Spectrum Absorption-line spectrum for Hydrogen Emission-line spectrum for Hydrogen

Our Sun’s Spectrum All of the dark lines represent the different elements in our Sun (67 or so)

Doppler Effect Waves are compressed and stretched depending on how the source is moving

Doppler Effect Blue Shift Red Shift Coming towards Going away

In your ISN Label the electromagnetic spectrum (Include wavelengths, frequency, types of radiation, and an example for each) Draw and label a continuous line spectrum, absorption, and emission line spectrum