Lecture 6 - Lecture 6 > Optics > Reflection ... Ray Optics 2 > Light travels in straight lines > Light

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  • Lecture 6

    > Optics

    > Reflection & Refraction

    Giancoli, Physics 6/e Serway & Vuille, College Physics 8/e Serway & Jewett, Physics for Scientists & Engineers, 6/e Tippens, Physics 7/e Young, Freedman & Ford, University Physics 14/e

    1 Villacorta--DLSUM-SCITECS-L06-1718Term03

  • Ray Optics

    2

    > Light travels in straight lines

    > Light propagation can be illustrated using rays, showing their direction as it travels through space.

    > Geometric optics refers to studying light propagation using the rays and angles

    Villacorta--DLSUM-SCITECS-L06-1718Term03

  • Reflection

    3

    > Shiny objects reflect light that hits it

    > Angle of incidence, angle of reflection + Light bounces back at the same angle that it hit the object + Optical plane + Surface normal + Law of reflection

    > Types of reflections + Diffuse: scattered, uneven, rough surface + Specular: mirror, image formation

    > Images: plane mirrors + Virtual image: can't be projected + Real image: can be projected

    Villacorta--DLSUM-SCITECS-L06-1718Term03 Johan Arvelius https://en.wikipedia.org/wiki/File:Reflection_angles.svg

  • Refraction

    4

    > Light travels slower through a medium than through vacuum: the ratio of these speeds is the index of refraction of the material

    n= c

    v

    boomeria.org

    Villacorta--DLSUM-SCITECS-L06-1718Term03 https://en.wikipedia.org/wiki/File:Snells_law.svg

  • Refraction contd.

    5

    > When light passes through a material, it bends due to traveling at a different speed: the relationship is given by Snell's law

    Willebrord Snellius 1580-1626

    wikipedia.orgagilescientific.com

    n1 sin θ1=n2 sin θ2

    Villacorta--DLSUM-SCITECS-L06-1718Term03

  • Total Internal Reflection

    6

    > When light goes from a slow medium to a fast one, it is possible for the light to be reflected inward and NOT refract into the second faster medium.

    > This occurs at a given critical angle θ C

    for material

    > Fiber optic cables work in this manner.

    ualberta.caVillacorta--DLSUM-SCITECS-L06-1718Term03

  • Ray Tracing

    7

    > Images are formed by light rays intersecting + Real image: intersection of reflected or refracted light rays + Virtual images: intersection of the projections of reflected or refracted light rays

    > The place where the image will form is the image distance: + It can be farther + or nearer to the mirror or lens

    > The image can also be: + Magnified + or shrunk

    Villacorta--DLSUM-SCITECS-L06-1718Term03

  • Mirrors

    8

    > The principal axis goes through the center of the mirror.

    > The center represents the center of a circle that the mirror is part of.

    > The focus is approximately located halfway between the center and the mirror.

    langlopress.net

    > Light rays passing through the center bounce off the mirror, passing through the center again.

    > Light rays passing through the focus bounce off the mirror, parallel to the principal axis.

    > Light rays initially parallel to the principal axis bounce off the mirror passing through the focus.

    Villacorta--DLSUM-SCITECS-L06-1718Term03

  • Mirrors contd.

    9

    * q > 0 if the reflected or refracted rays are on the same side as the focus

    * q < 0 if the reflected or refracted rays are on the opposite side as the focus

    langlopress.net

    1

    p +

    1

    q =

    1

    f

    m= image ht

    object ht =

    �q

    s

    Villacorta--DLSUM-SCITECS-L06-1718Term03

  • Mirrors contd.

    10

    * q > 0 if the reflected or refracted rays are on the same side as the focus

    * q < 0 if the reflected or refracted rays are on the opposite side as the focus

    langlopress.net

    1

    p +

    1

    q =

    1

    f

    m= image ht

    object ht =

    �q

    s

    Villacorta--DLSUM-SCITECS-L06-1718Term03

  • Summary

    11

    > Light travels in straight lines

    > Light can be reflected off a surface or refracted through a medium

    Mirrors can make images from light rays that bounce off it

    Villacorta--DLSUM-SCITECS-L06-1718Term03