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Chapter 14: Light and Reflection The Sombrero Galaxy (nasaimages)

Chapter 14: Light and Reflection The Sombrero Galaxy (www.nasaimages.org). Electromagnetic Waves. What’s comes to mind when you think of the word light? Generally people only think about sources that produce light that is visible to humans. What is light?.

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Chapter 14: Light and Reflection The Sombrero Galaxy (nasaimages)

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  1. Chapter 14: Light and Reflection The Sombrero Galaxy (www.nasaimages.org)

  2. Electromagnetic Waves • What’s comes to mind when you think of the word light? • Generally people only think about sources that produce light that is visible to humans

  3. What is light? • Light waves are electromagnetic waves • Remember that electromagnetic waves do not need a medium to propagate • Electromagnetic Wave: A transverse wave consisting of oscillating electric and magnetic fields at right anglesto each other.

  4. EM Waves

  5. There’s more than what the eye can see • Not all light is visible to the human eye • The complete electromagnetic spectrum contains many different types of radiation

  6. The electromagnetic spectrum

  7. Remembering the Spectrum • Rabbits Mate In Very Unusual Expensive Gardens • Red Martians Invaded Venus Using X-Ray Guns • From Longest Wavelength to Shortest Wavelength: Radio, Microwave, Infrared, Visible, Ultraviolet, X-Ray, Gamma Ray

  8. Why can’t we see the other parts of the EM spectrum? • The Sun’s surface is brightest in the portion of the spectrum that is visible to humans http://apollo.lsc.vsc.edu/classes/met130/notes/chapter2/plank_e_sun.html

  9. Microwave/Radio X Rays Ultraviolet Infrared Ultraviolet Does the Sun emit more than visible light radiation? White Light http://sohowww.nascom.nasa.gov/

  10. The Milky Way

  11. Galaxy M101 Across the Spectrum

  12. All EM waves travel at the speed of light • Speed of light in a vacuum: c= 3.00 x 108 m/s • Speed of light = frequency x wavelength

  13. Brightness • Brightness at any point is the power per unit area at that point (like sound intensity) • Brightness decreases by the square of the distance from the source • i.e. if you move an object twice as far away from a light source, one-fourth as muchlight falls on it

  14. How bright? • Let’s pretend that a person is looking at a candle that is 1 m away from her. If the candle were move to a distance of 3 m away, how would the brightness change? • The candle would be 1/9 as bright

  15. Section 14.2: Flat Mirrors • Reflection:The turning back of an electromagnetic wave at the surface of a substance

  16. Enceladus(Moon of Saturn) • Reflects ~ 99% of EM waves

  17. Iapetus (Moon of Saturn) • Light regions: Reflect 50-60% of EM Waves • Dark Regions: Reflect 2-5% of EM Waves

  18. Reflection • The texture of a surface affects how it reflects light • Diffuse Reflection:Rough, textured surfaces reflect light in many different directions • Specular Reflection:Smooth, shiny surfaces (i.e. water) reflect light in one direction

  19. Specular vs Diffuse Reflection • When the book says reflection, it means specular reflection

  20. Basic Reflection • Angle of Incidence (θ) = Angle of Reflection (θ’)

  21. Angles Angle of Incidence: (θ) The angle between the incoming light ray and the line perpendicular to the surface Angle of Reflection: (θ’) The angle between the reflected light ray and the line perpendicular to the surface

  22. Flat Mirrors • Flat Mirrors are the simplest type of mirror • When an object is placed in front of a flat mirror, light rays will spread out from the object and reflect from the mirror’s surface • Virtual Image: An image formed by light rays that only appear to intersect

  23. Flat (Plane) Mirror Images • The image produced is upright • The image is the same size as the object (i.e., the magnification is m = 1) • The image is the same distance from the mirror as the object appears to be (i.e., the image distance = the object distance) • The image is a virtual image

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