It is a stream of photons that

Each traveling in a wave-like pattern at right anglesMoving at the speed of lightCarrying some amount of energy.

What is Electromagnetic radiation

They differ in the amount of energy of the photons.

Wave-particle duality of light:

Light behaves like a wave and particle

Trend: Low energy photons behave more like waves while higher energy photons behave more like particles.

This affects how detectors and telescopes are designed to try to 'see' EM radiation from very low to very high energies.

Wavelength (m)

Frequency (Hz)

Energy (J)

Radio > 1 x 10-1 < 3 x 109 < 2 x 10-24

Microwave

1 x 10-3 - 1 x 10-1

3 x 109 - 3 x 1011

2 x 10-24- 2 x 10-22

Infrared7 x 10-7 - 1 x

10-3 3 x 1011 - 4 x 1014

2 x 10-22 - 3 x 10-19

Optical4 x 10-7 - 7 x

10-7

4 x 1014 - 7.5 x 1014

3 x 10-19 - 5 x 10-19

UV1 x 10-8 - 4 x

10-7

7.5 x 1014 - 3 x 1016

5 x 10-19 - 2 x 10-17

X-ray1 x 10-11 - 1

x 10-8

3 x 1016 - 3 x 1019

2 x 10-17 - 2 x 10-14

Gamma-ray

< 1 x 10-11 > 3 x 1019 > 2 x 10-14

E = h x nu

Where E = EnergyH= Planck’s constant = 6.626 x 10-27 erg-secondsNu = Frequency

299,792,458 m/s

Sources of Radiowaves

1) Quasars: one of a class of blue celestial objects having the appearance of stars when viewed through a telescope and currently believed to be the most distant and most luminous objects in the universe

2) Radio galaxies.

Infrared cosmos

All objects emit infrared radiation.  Infrared detectors detect wavelengths which are between wavelengths of about 1 and 300 microns (a micron is one millionth of a meter) The human eye detects only 1% of light at 0.69 microns, and 0.01% at 0.75 microns, and so effectively cannot see wavelengths longer than about 0.75 microns unless the light source is extremely bright.

Detecting cool objectsExploring the early universe

Absorption of Electromagnetic wavesGamma and X-ray: Oxygen and NitrogenUV rays: Oxygen and OzoneInfrared waves: Water

Ultraviolet Waves

Effects: Sunburns and skin cancer

Sun at extreme UV wavelength

How earth glows in UV light

Hottest and the most active objects in the cosmos give off large amounts of ultraviolet energy.

Applications:

Discern the …

Chemical composition Densities Temperatures of the interstellar medium Temperature and composition of hot young

stars. Sterilise glassware

Signature of hotter objects

X-rays and Gamma rays

X rays and some gamma rays are produced throughout the universe by the same catastrophic astrophysical events, such as supernovas and black holes.

Measuring Cosmic Radiation

The infrared part of the spectrum is where the emission and absorption lines of virtually all molecules as well as numerous atoms and ions (electrically charged atoms) lie. Infrared spectroscopy is the primary way to detect these elements in space.

http://www.google.com.sg/imgres?imgurl=http://andyxl.files.wordpress.com/2007/06/agn-cartoon.jpg&imgrefurl=http://andyxl.wordpress.com/2007/06/08/quasars-donuts-and-the-unified-faith/&usg=__ziYqqxnLf0XHGkLRAMqStHSDsFQ=&h=273&w=375&sz=17&hl=en&start=0&zoom=1&tbnid=zNnFl80ttARxZM:&tbnh=155&tbnw=202&prev=/images%3Fq%3DQuasars%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26sa%3DX%26rls%3Dorg.mozilla:en-US:official%26biw%3D1280%26bih%3D619%26tbs%3Disch:1&um=1&itbs=1&iact=rc&dur=330&ei=-8N_TN6nPJD8vQOPs52FBA&oei=-8N_TN6nPJD8vQOPs52FBA&esq=1&page=1&ndsp=18&ved=1t:429,r:2,s:0&tx=128&ty=66

http://www.google.com.sg/imgres?imgurl=http://www.oulu.fi/astronomy/astrophysics/pr/cenA.jpg&imgrefurl=http://www.oulu.fi/astronomy/astrophysics/pr/head.html&usg=__tq1EZyUjYiC6lJ83noZWHC05dhs=&h=593&w=599&sz=31&hl=en&start=0&zoom=1&tbnid=HsJZeb0Ix9Y8ZM:&tbnh=160&tbnw=167&prev=/images%3Fq%3DRadio%2Bgalaxies%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26sa%3DN%26rls%3Dorg.mozilla:en-US:official%26biw%3D1280%26bih%3D619%26tbs%3Disch:1&um=1&itbs=1&iact=rc&dur=366&ei=2cR_TKTYHY-CvgO4x-iQBA&oei=2cR_TKTYHY-CvgO4x-iQBA&esq=1&page=1&ndsp=18&ved=1t:429,r:0,s:0&tx=118&ty=41

http://www.infoplease.com/ce6/sci/A0840734.html#axzz0yO2QxXMC

http://science.hq.nasa.gov/kids/imagers/ems/uv.html

http://2010smtpsec3.wikispaces.com/Ace+Suggestions

http://www.windows2universe.org/physical_science/magnetism/em_ultraviolet.html

http://www.answers.com/topic/gamma-ray-astronomy