Unit 09 -- Light

1. absorption -- the taking in of energy of an electromagnetic wave by using that energy to boost an electron from a lower state to a higher one. color how human brains perceive different light frequencies.
2. concave mirror -- a reflective surface that bends inward at the middle; a type of converging mirror
3. constructive interference -- when two or more waves move through the same region of a medium, their amplitudes add together; this results in a larger amplitude than any of the constituent waves alone. converging a mirror or lens that focuses light together.
4. convex mirror -- a reflective surface that bulges outward in the middle; a type of diverging mirror
5. destructive interference -- when two or more waves move through the same region of a medium, their amplitudes add together; this results in a smaller amplitude than any of the constituent waves alone.
6. diffraction -- the spreading of waves around edges and barriers
7. diffuse reflection -- reflection off a surface in random directions; the type of reflection of light off objects in which you cannot see a clear image. diverging a mirror or lens that spreads light apart.
8. electromagnetic wave -- an energy-carrying wave emitted by a vibrating charge (often electrons) that is composed of oscillating electric and magnetic fields.
9. frequency -- the number of wave oscillations per second.
10. gamma rays -- highest energy type of e-m radiation; radiation that is only stopped by very dense materials; a type of ionizing radiation.
11. Hertz -- a shorthand unit for "waves per second".
12. infrared waves -- e-m radiation with wavelengths slightly longer than visible light; the type of radiation given off by everyday objects at everyday temperatures.
13. interference -- pattern a pattern in which waves constructively and destructively interfere, causing repeating bright and dark regions (if using light waves).
14. law of reflection -- the angle of incidence (away from the perpendicular) is equal to the angle of reflection.
15. lens -- a material shaped in such a way to bend light to a useful purpose.
16. light -- energy the energy captured in a photon; equivalent to the product of Planck's constant and the frequency.
17. LOST -- an acronym that describes the most important qualities of an image: Location, Orientation, Size, and Type.
18. medium -- the stuff that a wave moves through.
19. microwaves -- the second longest wavelength e-m radiation; used for communication, for cooking, and deep-sky astronomy.
20. nanometer -- equivalent to 10^-9 m; a unit that is more useful to physicists studying light waves.
21. opaque -- a material in which light is absorbed and not quickly released.
22. Planck's constant -- a conversion factor between Hertz and Joules, specific to light.
23. plane mirror -- a reflective surface with a flat edge.
24. polarization -- the blocking/filtering of light waves that are not parallel to a given axis.
25. radio waves -- the longest wavelength e-m radiation; often used for communication due to its low energy and ability to move easily through the atmosphere.
26. ray diagram -- a diagram in which light rays move in straight lines from an object toward a mirror or lens; these diagrams are used to determine the nature of the image produced by a mirror or lens.
27. re-emission -- the release of energy in the form of a photon when an electron moves from a higher state to a lower one; the energy released is equal to the energy absorbed when the electron is pushed to to higher state.
28. real image -- an image that exists in real space; an image that can be projected on a screen.
29. reflection -- the bouncing of waves off of barriers; the rule determining the way barriers reflect is the law of reflection.
30. refraction -- the bending of waves due to the change in average speed of those waves due to a change in the medium.
31. resonance -- the increased amplitude of vibration of an object, a substance, a molecule or an atom in response to the presence of a wave of the same frequency.
32. scattering -- the deflection of light waves in random directions by particles in a substance; the wavelengths of light that are scattered depend on the size of the particles doing the scattering.
33. spectral absorption -- lines the wavelengths (energies) of light that are absorbed in a hot body's spectrum; the specific wavelengths of light are absorbed by specific atoms and molecules, giving clues to the types of atoms and molecules present.
34. spectrum -- a range of frequencies of electromagnetic radiation.
35. specular reflection -- reflection of parallel rays off a surface such that they remain parallel after reflection; the type of reflection of light found in mirrors and other highly reflective objects. speed the distance a wave travels in one second.
36. transparent -- a material in which light is absorbed and quickly released in the same direction.
37. ultraviolet rays -- type of e-m radiation that has wavelengths shorter than visible light; a type of ionizing radiation; this type of radiation can cause skin cancer and can be used to destroy bacteria and other germs.
38. virtual image -- an image that only exists in virtual space; an image that cannot be projected on a screen.
39. visible light -- waves e-m radiation to which our atmosphere is most transparent; this range lies at the middle of the electromagnetic spectrum; organisms use it to sense their environments.
40. wave behaviors -- behaviors that are unique to waves, including refraction, diffraction and interference.
41. wave-particle duality -- the true nature of light; the theory that light behaves as a photon and also as a wave moving through electric and magnetic fields.
42. wavelength -- the distance between two similar successive points on a wave, e.g. crest to crest or trough to trough.
43. x-rays -- type of e-m radiation that has enough energy to penetrate through soft tissues; a type of ionizing radiation; is often used in the medical field.

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