Optics In this unit: Properties of light Reflection Lenses And applications of optics Refraction

Recap of Light Light travels in straight lines – until bent when passing through a different substance - REFRACTION Light travels much faster than sound Light is either reflected or absorbed We see things because they reflect light into our eyes Objects can be Luminous or non-luminous

Recap of Light Light Form of energy – specifically the electron movement from one orbital shell to another Visible Light Spectrum of energy wavelengths that the human eye can detect Light Sources (11.1, 11.2) Fluorescence, incandescent, bioluminescence, chemiluminescence, etc

Reflection Terminology Reflection from a mirror: Normal Incident ray Reflected ray Angle of incidence Angle of reflection Mirror

Clear vs. Diffuse Reflection Specular Reflection: Smooth, shiny surfaces have a clear reflection: Rough, dull surfaces have a diffuse reflection. Diffuse reflection is when light is scattered in different directions

Clear vs. Diffuse Reflection

converge: come together We see images when light rays converge in our eyes. converge: come together

Yesterday you learned how to draw images in a Plane Mirror Draw line & measure Repeat lines behind mirror 2cm 2cm object 3.5cm 3.5cm mirror

Characteristics of images in plane mirrors The image in a plane mirror is always Same size as the object Upright, inverted laterally Behind the mirror and Virtual (an image formed in a location that the light does not actually reach)

Forming Images with a Plane Mirror Light reflected from the flower and vase hits the mirror. Obeying the law of reflection, it enters the eye. The eye interprets the ray as having had a straight-line path, and sees the image behind the mirror.

Plane Mirrors (flat mirrors) How do we see images in mirrors?

Plane Mirrors (flat mirrors) object image How do we see images in mirrors? Light reflected off the mirror converges to form an image in the eye.

Plane Mirrors (flat mirrors) object image How do we see images in mirrors? Light reflected off the mirror converges to form an image in the eye. The eye perceives light rays as if they came through the mirror. Imaginary light rays extended behind mirrors are called sight lines.

Steps for drawing Plane Mirror Ray Diagrams: 1. A ray that strikes perpendicular to the mirror surface, reflects perpendicular to the mirror. The reflected ray is extended beyond the mirror. 2. A ray that strikes the mirror at any angle reflects so the angle of incidence equals the angle of reflection. The reflected ray is extended beyond the mirror.

Using Ray diagrams draw a ray diagram to show how Suzie will be able to see the image of the green object arrow in the diagram (this is a proof)

The four steps of the process Draw the image of the object. Use the principle that the object distance is equal to the image distance to determine the exact location of the object

2. Pick one extreme on the image of the object and draw the reflected ray that will travel to the eye as it sights at this point.

3.Draw the incident ray for light traveling from the corresponding extreme on the object to the mirror.

4. Repeat steps 2 and 3 for all other extremities on the object.

Examples

Uses of Ray Diagrams Ray diagrams are useful tools for determining and explaining what objects might be viewed from certain locations For example, suppose that six students - Al, Bo, Cy, Di, Ed, and Fred sit in front of a plane mirror and attempt to see each other in the mirror

Yesterday’s Handout – Activity 1 Whom can Al see? Whom can Bo see? Whom can Cy see? Whom can Di see? Whom can Ed see? And whom can Fred see?

First step is to draw out where you know the images will be First step is to draw out where you know the images will be. Then use ray diagrams to figure out who each person can see.

Activity 2 P489 TRY THIS “producing images” Text work: P493 #1,3,7,9

Activity 3 – New handout A periscope: Utilizes mirrors to help view around objects – such as tank commanders to inspect their situation without leaving the safety of the tank or in a submarine A periscope

Using Plane Mirrors The kaleidoscope – fun uses of plane mirrors

First Al is isolated from the rest of the students and lines of sight are drawn to see who Al can see Al’s lines of sight are limited by the edges of the mirror. Only Ed and Fred are within these sight lines.

Bo can see Di, Ed, and Fred Cy can see Cy, Di, Ed, and Fred Di can see Cy, Di, Ed, and Fred Ed can see Bo, Cy, Di, and Eve Fred can see Al, Bo, Cy, and Di