Electromagnetic Wave

1. Electromagnetic wave- a wave produced by the acceleration of an electric charge and propagated by the periodic variation of intensities of, usually, perpendicular electric and magnetic fields.

2. Transverse wave- a wave in which the direction of displacement is perpendicular to the direction of propagation, as a surface wave of water.

3. Speed of light in vacuum- the constancy and universality of the speed of light is recognized by defining it to be exactly 299,792,458 meters per second.

4. Electromagnetic spectrum- the entire range of wavelengths or frequencies of electromagnetic radiation extending from gamma rays to the longest radio waves and including visible light.

5. Frequency of light- light is a wave, waves have frequency and wavelength. The frequency and wavelength correspond physically to the colors we see

6. Polarization- the process in which the waves of light or other electromagnetic radiation are restricted to certain directions of vibration usually specified in terms of the electric field vector.

7. Reflection- the change in direction of a wave, such as a light or sound wave, away from a boundary the wave encounters.

8. Visible light- electromagnetic radiation that can produce a visual sensation.

9. Light ray- a beam of light having a small cross section.

10. Law of reflection- the principle that when a ray of light, radar pulse, or the like, is reflected from a smooth surface the angle of reflection is equal to the angle of incidence, and the incident ray, the reflected ray, and the normal to the surface at the point of incidence all lie in the same plane.

11. Angel of reflection- the angle that a ray of light or the like, reflected from a surface, makes with a normal to the surface at the point of reflection.

12. Angel of incidence- the angle formed by a ray or wave, as of light or sound, striking a surface and a line perpendicular to the surface at the point of impact.

13. Virtual image- an optical image formed by the apparent divergence of rays from a point, rather than their actual divergence from a point

14. Real image- an optical image formed of real foci

15. Specular reflection- reflection of electromagnetic, acoustic, or water waves in which the reflected waves travel in a definite direction, and the directions of the incident and reflected waves make equal angles with a line perpendicular to the reflecting surface, and lie in the same plane with it

16. Diffuse reflection- reflection of light, sound, or radio waves from a surface in all directions according to the cosine law.

17. Plane mirror- a mirror whose surface lies in a plane; it forms an image of an object such that the mirror surface is perpendicular to and bisects the line joining all corresponding object-image points.

18. Concave mirror- mirror that converges parallel light rays on its surface.

19. Convex mirror- mirror that diverges parallel light rays on its surface.

20. Principal Axis- one of three mutually perpendicular axes of a body about which the moment of inertia is maximum or minimum.

21. Focal point- either of two points on the axis of a mirror, lens, or other optical system, one point being such that rays diverging from it are deviated parallel to the axis upon refraction or reflection by the system and the other point being such that rays parallel to the axis of the system converge to the point upon refraction or reflection by the system.