Chapter 14 Light and Reflection Holt Physics Chapter 14 Light and Reflection

14-1 Electromagnetic Waves A transverse wave consisting of oscillating electric and magnetic fields at right angles to each other.

14-1 Electromagnetic Spectrum (SciLinks: HF2141, Electromagnetic Spectrum)

14-1 Wave Equation for Light c = f c = speed of all electromagnetic waves = 3.00  108 m/s The AM radio band extends from 5.4 x 105 Hz to 1.7 x 106 Hz. What are the longest and shortest wavelengths in this frequency range. F1 = 5.4 x 105Hz F2 = 1.7 x 106 Hz C = 3.00 x 108 m/s 1 = ? 2 = ? c = f 1 = c/f = (3.00 x 108 m/s)/(5.4 x 105 Hz) = 5.6 x 102 m 2 = c/f = (3.00 x 108 m/s)/(1.7 x 106 Hz) = 1.8 x 102 m

14-1 Huygen’s Principle A wave front can be divided into point sources. The line tangent to the wavelets from these sources marks the wave front’s new position. Ray approximation: a method of treating a propagating wave as a straight line perpendicular to the wave front.

14-1 Light Brightness Brightness  1/d2

14-1 Review | Assignment If an electromagnetic wave has a frequency of 7.57  1014 Hz, what is its wavelength? To what part of the spectrum does this wave belong? Galileo performed an exper9iment to measure the speed of light by timing how long it took light to travel from a lamp he was holding to an assistant about 1.5 km away and back again. Why was Galileo unable to conclude that

14-2 Reflection The turning back of an electromagnetic wave at the surface of a substance. Diffuse: irregular reflection Specular: smooth shiny surfaces

14-2 Law of Reflection Incoming and Reflected angles are equal. Angle of Incidence: the angle between a ray that strikes a surface and the normal to that surface at the point of contact. Angle of Reflection: the angle formed by the line normal to a surface and the direction in which a reflected ray moves.

14-2 Plane Mirrors Produce virtual images that are the same size and distance from the mirror. (SciLinks: HF2143, Mirrors) Image can be located using a ray diagram

14-2 Review | Assignment Which of the following are examples of specular reflection and which are examples of diffuse reflection? Reflection of light from the surface of a lake on a calm day Reflection of light from a plastic trash bag Reflection of light from the lens of eyeglasses Reflection of light from a carpet If one wall of a room consists of a large flat mirror, how much larger will the room appear to be? Explain your answer. Why does a flat mirror appear to reverse images left to right, but not up and down?

14-3 Concave Spherical Mirror An inwardly curved, mirrored surface that is a portion of a sphere and that converges incoming light rays. Form real images

14-3 Mirror Equation 1/p + 1/q = 1/f p = object distance q = image distance f = focal length

14-3 Magnification Equation M = h’ / h = -q/p h’ = image height h = object height

14-3 Rules for Drawing Reference Rays Check out Holt Physics Interactive Tutor CD-ROM Module 14: Reflection and Mirrors

14-3 Object located beyond Center of Curvature

14-3 Object located at Focal Point

14-3 Object located in front of Focal Point

14-3 Concave Mirror Problem A concave spherical mirror has a focal length of 10.0 cm. Locate the image of a pencil that is placed 30.0 cm from the mirror. Find the magnification of the image. Draw a ray diagram to confirm your answer. F = +10.0 cm P = +30.0 cm Q = ? M = ? 1/p + 1/q = 1/f 1/q = 1/f – 1/p = 1/10.0 cm – 1/30.0 cm = 15 cm. M = -1/p = -(15cm/30.0 cm) = -0.50 Real image reduced in size.

14-3 Convex Spherical Mirrors An outwardly curved, mirrored surface that is a portion of a sphere and that diverges incoming light rays. Forms virtual, reduced images.

14-3 Sign Conventions

14-3 Sign Conventions

14-3 Convex Mirror Problem An upright pencil is placed in front of a convex spherical mirror with a focal length of 8.00 cm. An erect image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil. F = - 8.00 cm Q = -4.44 cm H’ = 2.50 cm P = ? H = ? 1/p = 1/f – 1/q = (1/-8.00 cm) – (1/-4.44 cm) = 10.0 cm M = -(1/p) = -(10.0 cm/-4.44 cm) = 5.63 cm

14-3 Parabolic Mirror A mirror in which all parallel rays converge at the focal point. Eliminates spherical aberration. (SciLinks: HF2144, Telescopes)

14-3 Review | Assignment Why is an image formed by a parabolic mirror brighter than the image of the same object formed by a concave spherical mirror? A spherical mirror is to be used in a motion-picture projector to form an inverted, real image 95 times as tall as the picture in a single frame of film. The image is projected onto a screen 13 m from the mirror. What type of mirror is required, and how far should it be from the film? Which of the following images are real and which are virtual? The image of a distant illuminated building projected onto a piece of heavy, white cardboard by a small reflecting telescope The image of an automobile in a flat rearview mirror The image of shop aisles in a convex observation mirror

14-4 Colors of Light Additive Process: Primary Colors are added to produce white light. (SciLinks: HF2145, Color)

14-4 Colors of Pigments Pigments absorb certain colors. You see only the colors that are reflected.

14-4 Seeing Colors You see the colors that are reflected or transmitted to your eye. Cones: color sensitive cells. Pixels: luminous dots of blue, green, and red light.

14-4 Primary/Complementary Colors

14-4 Polarization of Light The alignment of electromagnetic waves in such a way that the vibrations of the electric fields in each of the waves are parallel to each other.

14-4 Polarizing Sunglasses

14-4 Review | Assignment A lens for a spotlight is coated so that it does not transmit yellow light. If the light source is white, what color is the spotlight? A house is painted with pigments that reflect red and blue light but absorb all other colors. What color does the house appear to be when it is illuminated by white light? What color does it appear to be under red light? The light reflected from the surface of a pool of water is observed through a polarizer. How can you tell if the reflected light is polarized?