Transcript Slide 1
Color Color we see depends on frequency of light ranging from lowest (red) to highest (violet). In between are colors of the rainbow. Hues in seven colors: red, orange, yellow, green, blue, indigo, and violet. Grouped together, they add to appear white. Selective Reflection Most objects don’t emit light, but reflect light. A material may absorb some of the light and reflect the rest. The color of an opaque object depends on the color of the light it reflects. Selective Transmission The color of a transparent object depends on the color of the light it transmits . Additive Primary Colors Any three colors that, when added up, can generate the entire spectrum of colors. Common Additive Primary Colors (red, blue, green): red + blue = magenta red + green = yellow blue + green = cyan Subtractive Primary Colors Questions? Optics Reflection the returning of a wave to the medium through which it came when encountering a reflective surface Virtual Image On a Plane Mirror - same size as object - formed behind the mirror - as far behind the mirror as the object is in front of the mirror - the front-back axis is reversed Curved mirrors form a different virtual image… • convex mirror : virtual image is smaller and closer to the mirror than the object • concave mirror : virtual image is larger and farther away than the object Diffuse reflection Light striking a rough or irregular surface reflects in many directions. It is the way by which we see the world. Diffuse Reflection Application The open-mesh parabolic dish is a diffuse reflector for short-wavelength light. It is also a polished reflector for longwavelength radio waves. Refraction The bending of light when it passes from one medium to another. Caused by change in speed of light Illusions caused by refraction Objects submerged in water appear closer to the surface. Illusions caused by refraction Objects such as the Sun seen through air are displaced because of atmospheric refraction. Illusions caused by refraction Atmospheric refraction is the cause of mirages. Dispersion Different frequencies of light are refracted at different angles. This allows us to disperse the components of white light using a prism or a diffraction grating. Dispersion CHECK YOUR NEIGHBOR When white light passes through a prism, green light is bent more than A. B. C. D. blue light. violet light. red light. None of the above. Dispersion CHECK YOUR ANSWER When white light passes through a prism, green light is bent more than A. B. C. D. blue light. violet light. red light. None of the above Rainbows are a colorful example of dispersion. Rainbow Facts Geometric Optics Polarization Polarization alignment of transverse electric vectors in electromagnetic waves property of transverse waves Left: E & M wave is polarized Right: rope vibrations are polarized In both cases, wave is in the same plane as the plane of vibration. Polarization Unpolarized light vibrations producing light are in random directions Polarization Polarized light Unpolarized light divided into two internal beams polarized at right angles to each other. One beam is absorbed while the other beam is transmitted. Polarization Polarized light (continued) Use your knowledge of vectors and vector components to explain how light that can’t pass through a pair of Polaroids at right angles to each other will pass light when a third Polaroid is sandwiched between them! end