Slide 1

Slide 2 The Physics of the Electromagnetic Spectrum or Radiant Energy *** Light, Heat, and Radiation Slide 3 Light = EM Spectrum The terms light, radiation, and electromagnetic wave are the same thing. Light comes in many forms. This is something that science did not understand until recently. X-rays, visible light, radio waves are all the same thing. They just look different. We only see visible light, but we have learned to make tools that let us see other types of light. Jupiter seen at different wavelengths of light Slide 4 Key concepts: EM spectrum Visible light ROY G BIV Light is fast and travels straight Light acts like a Wave & Particle Reflection/Refraction/Diffusion Opaque/translucent/transparent Primary colors Wavelength/Frequency/Amplitude Slide 5 Slide 6 Visible Light Slide 7 Isaac Newton (1642 1727) Christiaan Huygens 1629 -1695) The Fathers of the Science of Light Slide 8 VISIBLE LIGHT IS ONLY A SMALL PART OF THE ELECTROMAGNETIC SPECTRUM Slide 9 WHITE LIGHT IS ACTUALLY MADE OF THE COLORS OF THE RAINBOW MIXED TOGETHER BLACK IS THE ABSENCE OF LIGHT Slide 10 Light travels in a straight line from its source Slide 11 Light travels in a straight line very fast, and forever Light is the fastest thing we know of in the universe. It sets the universal speed limit 186,000 miles per SECOND In the vacuum of space Slide 12 That is 672,000,000 miles per hour Slide 13 That is 5.87910 12 5,879,000,000,000 or in regular numbers miles per year Five Trillion, eight hundred seventy nine billion Slide 14 This is called a light year 5,879,000,000,000 miles is a common unit of astronomical distance measurement Slide 15 Some interesting distances Slide 16 Light also travels forever, and if its source is strong enough, we can see it. Slide 17 The nearest star to our sun is Proxima Centauri It is 4.2 light-years distant in the constellation of Centaurus Slide 18 Say hello to the super nova GRB 080319B, the brightest and most distant object we know of in the universe. Slide 19 Astronomers have placed the star in the constellation Botes. They have estimated it to be 7.5 billion light years away from Earth, meaning the explosion took place when the universe was less than half its current age and before Earth formed. Slide 20 It is calculated to be 2.5 million times brighter than the brightest supernova ever recorded before it. Slide 21 GRB 080319B is an example of how far light can travel and also of how vast the universe really is Slide 22 Light has a strange combination of properties Light Acts Like a Wave It also acts like a stream of particles Slide 23 Particle Stream Slide 24 Waves Key concepts Wavelength Amplitude Frequency These words have the same meaning as in the study of sound. Slide 25 Frequency = number of waves that pass a point in a certain time We usually measure it in Cycles per Second or Hertz (Hz) Slide 26 Wave Terminology Wavelength - distance between two like points on the wave Amplitude - the height of the wave compared to undisturbed state Period - the amount of time required for one wavelength to pass Frequency - the number of waves passing in a given amount of time Slide 27 Light has Certain Behaviors Reflection Refraction Diffraction Slide 28 LIGHT can be REFLECTED - Reflection is light bouncing off of a smooth shiny surface. Slide 29 Reflection is Light Bouncing off a shiny surface A B X Y Angle A = Angle B and Angle X = Angle Y Angle of Incidence Angle of Reflectance Slide 30 Light Can Be Bent Refraction (or bending) of light happens when light passes through transparent materials of different density Slide 31 Slide 32 Slide 33 Refraction lets us make lenses Slide 34 Diffraction just a touch of information Slide 35 White light is made of many wavelengths of light. Each wavelength is a different color of light. When they are all seen together, we see them as white light. Slide 36 Each Wavelength Refracts differently Slide 37 Because of this, refraction permits us to split white light into its colors ROYGBIVROYGBIV Slide 38 Red Orange Yellow Green Blue Violet ROY G BV Slide 39 How Roy G. Bv Lost a Vowel The sequence of colors red, orange, yellow, green, blue, and violet may be remembered by memorizing the name of that fine fellow "ROY G. BV". This was originally "ROY G. BIV", because it used to be common to call the region between blue and violet "indigo". In modern usage, indigo is not usually distinguished as a separate color in the visible spectrum; thus Roy no longer has any vowels in his last name. Slide 40 LASER Slide 41 "Laser" is an acronym for light amplification by stimulated emission of radiation Slide 42 Slide 43 Slide 44 Slide 45 Slide 46 Primary Colors of LIGHT not pigments Red Green Blue Slide 47 The colors we see in objects are the colors that are reflected, all other colors are absorbed. A red t-shirt appears red because red is reflected to our eyes and the other colors are absorbed. When all colors are being reflected we see white light (white isnt really a color) Slide 48 When all wavelengths of light are being absorbed we see black (black also, isnt really a color) A false-color image is made when the satellite records data about brightness of the light waves reflecting off the Earth's surface. Slide 49 Diffusion When Light Hits Uneven Surfaces Slide 50 LIGHT BOUNCING OFF OF WHITE PAPER = EXAMPLE OF DIFFUSION Slide 51 Important Terms Opaque Translucent Transparent Slide 52 The Rest of the Electromagnetic Spectrum Slide 53 Microwaves Slide 54 Infrared Slide 55 UV Slide 56 X-ray Slide 57 The shortest and most dangerous radiation Slide 58 Slide 59 Gamma ray burns from the Hiroshima bomb. Slide 60 Understanding the EM Spectrum lets us See Thing in a Different Light. Slide 61 The Sun at Different Wavelengths VisibleUltraviolet X-ray Slide 62 Atoms and Light The movement of electrons inside of atoms produces light and other electromagnetic radiation. Sunlight produces every color in the rainbow but Each element gives off only certain frequencies of light, called spectral lines. In effect each element has its own signature of spectral lines allowing us to identify which element we have or what stars are made of. Slide 63 Below is a picture of the spectral lines given off by hydrogen. Note there are 3 different frequencies. Slide 64 Key concepts: Waves and particles EM spectrum Visible light ROYGBIV Reflection/Refraction/Diffusion Opaque/translucent/transparent Primary colors Wavelength/Frequency/Amplitude