2 Electromagnetic Wave Properties Electromagnetic waves do not need a medium to propagate. They can travel in a vacuum.The speed of all electromagnetic radiation in a vacuum is a constant.c = 3 X 108 m/s.
3 Electromagnetic Spectrum Draw out the spectrum noting trends in frequency, wavelength, wave speed and energy.There is a easy mnemonic to help you remember the order of EM radiation….Red Martians Invade Venus Using X-ray GunsRadio, Microwave, Infrared, Visible, Ultraviolet, X-ray, GammaWavelength…Starts Long and gets shorter towards GammaFrequency……Starts Low and gets higher towards GammaSpeed is the same for all EM wavesEnergy…Starts low and gets higher towards Gamma
4 Visible Light Colors Addition vs. Subtraction of Color The perceived color of an object is due to two processes, addition and subtraction of colors.The addition of color is the projection of various intensities of the primary colors of light to produce the desired color.The subtraction of color is the absorption of specific colors by pigments. The colors that remain produce the desired color. The reflection of white light off a colored object is an example of color subtraction.
10 Reflection Definition of Reflection The turning back of a wave. Law of ReflectionAngle of Incidence = Angle of Reflection.i = r or ‘theta’ is a symbol used to denote a variable angle.(It is like ‘x’ in algebra.)
11 Refraction Definition of Refraction Definition of Index of Refraction The bending of a wave disturbance as it passes at an angle from one medium to another due to a change in speed.Definition of Index of RefractionThe ratio of speed of light in a vacuum to its speed in a given transparent medium.
12 Index of Refraction of Common Items VacuumAir(we round to 1.0)WaterCommon Glass 1.5Diamond 2.42
13 Refraction Bending Rules The ray bends towards the normal, ni < nr. Light traveling from a less dense to more dense medium slows down.The ray bends towards the normal,ni < nr.Light traveling from a more dense to less dense medium speeds up.The ray bends away from the normal,nr < ni.
14 ni sini = nr sinr Snell’s Law n = index of refraction = angle i = incident rayr = refracted ray
15 Example #1What is the index of refraction of a medium in which the speed of light is 1.85 X 108 m/s?
16 Example #2A fisherman shines a flashlight at a fish swimming underwater. If the refracted ray makes an angle of 35.0 with normal, what is the angle of incidence?
17 Total Internal Reflection Definition of Total Internal ReflectionThe complete reflection of light at the boundary of two transparent media. The effect occurs when the angle of incidence exceeds the critical angle for a light ray going from a more dense medium to a less dense medium.Definition of Critical AngleThe minimum angle of incidence for which total internal reflection occurs. This occurs when the angle of refraction becomes 900.
18 Lenses Convex Lens Converging Lens Focal Point Focal Length Real Image Location at which rays parallel to the principal axis converge to or appear to diverge from for a convex or concave lens respectively.Focal LengthDistance from the focal point to the center of the lens.Real ImageAn image formed when rays of light actually intersect at a single point.
19 Lenses Concave Lens Diverging Lens Focal Point Focal Length Location at which rays parallel to the principal axis converge to or appear to diverge from for a convex or concave lens respectively.Focal LengthDistance from the focal point to the center of the lens.Virtual ImageAn image formed by light rays that only appear to intersect
21 Ray Diagram Lens Trends Case Converging or Convex Lens Diverging or Concave LensSizeOrientationImagedo > 2fdo = 2f2f > do > fdo = fdo < f
22 Converging or Convex Lens Diverging of Concave Lens Ray DiagramLens TrendsConverging or Convex LensDiverging of Concave LensFocal LengthObject DistanceImageDistanceReal ImageVirtual ImageObject HeightImage Height
24 Example #4Example #4If an object is placed 15 cm in front of a converging lens with a focal length of 10 cm, how far from the lens should the card be placed in order to find a clear image?
25 Interference Interference Diffraction Polarization Doppler Effect Pattern of constructive and destructive interference.DiffractionThe spreading of waves into a region behind an obstacle.PolarizationThe alignment of electromagnetic waves.Doppler EffectA frequency shift that is the result of relative motion between the source of sound waves and an observer.