Laws of Reflection and Plane Mirror Images

Reflection When light strikes a surface, some is absorbed, the rest bounces off the surface. This is called reflection.

Reflection on Different Surfaces When the reflecting surface is rough, it produces a diffuse reflection.

Reflection on Different Surfaces When the reflecting surface is smooth, it produces a specular (uniform) reflection.

Reflecting Light Terms Incident Ray: Approaching ray Reflected Ray: Ray that the mirror reflects Point of Incidence: Place where incident ray strikes a mirror. Normal: Line at right angles to the surface of the mirror drawn at the point of incidence

Plane Mirror Incident Ray Normal Reflected Ray Plane Mirror Point of Incidence Reflected Ray

Reflecting Light Terms (cont.) Angle of Incidence (θi): Angle between the Incident Ray and the Normal Angle of Reflection (θr): Angle between the Reflected Ray and the Normal

Plane Mirror Incident Ray Angle of Incidence Angle of Reflection Reflected Ray

Laws of Reflection The Angle of Incidence is equal to the Angle of Reflection (θi = θr) The Incident Ray, the Reflected Ray and the Normal all lie in the same plane.

Images in a Flat Mirror An illuminated object gives off light in all directions, but you see only the rays coming toward you.

Flat or Plane Mirror Reflected object appears to be coming from the other side of the mirror.

Your brain does not process the fact that light has been reflected Assumes that light travels in a straight line. Assumes the origin of the rays is behind the mirror.

Image Characteristics of a Plane Mirror (SALT) Size: No magnification Attitude: (Orientation) Laterally inverted (left-right inverted) Location: Image distance is same as object distance Type: Image is virtual (cannot be focused on a screen)

Ray Diagrams A way to locate a virtual image do = object distance di = image distance For a plane mirror: do= di

Image Characteristics of a Plane Mirror (SALT) S: size of image a size comparison between the height of the image (hi) and the height of the object (ho) M = hi / ho = di / do A: attitude (orientation) of image – upright or inverted L: location of image (distance to the mirror) T: type of image (real or virtual) Virtual images are formed in locations where light does not actually reach Real images can be projected on a screen

Mirror image is laterally inverted. Ambulance Ambulance