Unit 3: Optics Chapter 4

History of Light https://www.youtube.com/watch?v=j1yiapztlos

History of Light Early philosophers (Pythagoras) believed light was made up of tiny particles Later scientist found evidence that light also behaved like a wave. We now understand that light can act both as a particle and a wave.

History of Light Light: A form of energy that can be described as both a wave and a particle. Visible light is a type of light that can be detected by the human eye.

History of Light Galileo was the first person to try to measure the speed of light 2 people stood on opposite hilltops with lanterns uncovered the lanterns, timed how long it took for the light to reach the other person used the distance between hilltops and the time to calculate the speed This experiment did not work Why?

History of Light Albert Michelson was the first person to successfully measure the speed of light Speed of light : 1 000 000 000 km/ hr Speed of sound 1 200 km/hr

History of Light In a storm, which do you experience first; the sight of the lightning or the sound of thunder? why?

Wave model of light Wave Model

Wave Model Terms: Crest: The highest point in a wave (the peak)

Wave Model Terms: Crest: The highest point in a wave (the peak) Trough: The lowest point in a wave

Wave Model Terms: Crest: The highest point in a wave (the peak) Trough: The lowest point in a wave Amplitude: The height of a wave. Measured form the rest position to the crest. measures the energy of the wave (higher amplitude= more energy)

Wave Model Terms: Wavelength: The length of one full wave. (from crest to crest or trough to trough) Usually measured in metres

Wave Model Terms: Wavelength: The length of one full wave. (from crest to crest or trough to trough) Usually measured in metres Frequency: The number of wavelengths that pass a point in 1 second Measured in Hertz (Hz) High frequency waves have shorter wavelengths Low frequency waves have longer wavelengths

Wave Model Label the waves on your worksheet and complete the measurements

Light Electromagnetic Spectrum: All of the different wavelengths of electromagnetic radiation (a type of energy) arranged from longest to shortest wavelength Cell Phones Cancer treatment

Light Visible Light In the middle of the electromagnetic spectrum The only wavelengths we can see with the human eye Visible Spectrum: ROY G BIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet)

Properties of Light In the previous class we experimented with light and saw how it interacted with different materials What observations did we make? How did light interact with each of the following? Mirrors Prisms Fabric Paper Solid objects Glass Water Spoon

Properties of Light Reflection- Light bounces off some surfaces (ex. Mirrors)

Properties of Light Reflection- Light bounces off some surfaces (ex. Mirrors) Refraction- Light bends as it moves form one material to another (ex light moving from air to water)

Properties of Light Reflection- Light bounces off some surfaces (ex. Mirrors) Refraction- Light bends as it moves form one material to another (ex light moving from air to water) Dispersion- Light can be separated into its different wavelengths or colours (ex. Rainbows)

Properties of Light Travels through a vacuum- Light can travel through empty space unlike sound which needs a medium (air or water) to travel through

Properties of Light Travels through a vacuum- Light can travel through empty space unlike sound which needs a medium (air or water) to travel through Rectilinear Propagation- Light travels in a straight line This created shadows

Properties of Light Absorption- Different materials absorb light by different amounts

Unit 3: Optics Chapter 5

Modeling Light Particle model- early scientist not wrong, explains some properties that a waves cannot

Modeling Light Particle model- early scientist not wrong, explains some properties that a waves cannot Wave model- accounts for different frequencies, wavelengths and therefore colour Light behaves like both a particle and a wave

Modeling Light Light behaves like both a particle and a wave - To simplify and help us understand how light behaves we use the Ray Model Ray model :represents light as a straight line or ray showing the direction of travel

Modeling Light We can use the ray model to show the different properties of light Rectilinear Propagation

Modeling Light Light travels through objects to different degrees distorted Images are

Modeling Light Transparent Clear windows Water Translucent Stained glass Frosted glass Wax paper Opaque Cardboard Wood

Modeling Light Reflection- light bounces off of a surface mirror

Modeling Light Refraction- light is bent as it passes through different mediums Air Water

Parts of a reflection diagram: Modeling Light Incident Ray: Incoming ray from the object into the mirror ormal Reflected Ray: Outgoing ray being reflected from the mirror

Parts of a reflection diagram: Modeling Light ormal Normal: Line drawn at right angle to the mirror Angle of incidents: Angle between incident ray and normal Angle of reflection: Angle between reflected ray and normal

Law of reflection Law of reflection: when a ray is reflected from a smooth surface the angle of reflection is equal to the angle of incidence Normal

Law of reflection Law of reflection: when a ray is reflected from a smooth surface the angle of reflection is equal to the angle of incidence Normal 40 0 40 0

Reflection Specular The two types of reflection; smooth surface rays remain together Calm water Plane mirrors Glossy photographs Diffuse rough surface rays are diffused in different directions Textured countertop Matte photographs

Types of Mirrors Plane Concave Convex Flat Surface curved inward curved outward

Examples: Bathroom mirror flashlight, projector bus mirrors security mirrors Types of Mirrors Plane Concave Convex Flat Surface curved inward curved outward

Types of Mirrors We draw ray diagrams of mirrors to see where and how an image will be reflected

Types of Mirrors We draw ray diagrams of mirrors to see where and how an image will be reflected Remember: Normal

Drawing a ray diagram for a plane mirror Rule: Angle of Incidents = Angel of Reflection 1. Draw a ray from the object into the mirror

Drawing a ray diagram for a plane mirror Rule: Angle of Incidents = Angel of Reflection 1. Draw a ray from 2.Draw a normal line at the object into the the point where the mirror ray hits the mirror 3.Measure the angle of incidence

Drawing a ray diagram for a plane mirror Rule: Angle of Incidents = Angel of Reflection 1. Draw a ray from 2.Draw a normal line at 4. Draw a reflected ray at the object into the the point where the the same angle mirror ray hits the mirror 3.Measure the angle of incidence

Drawing a ray diagram for a plane mirror Rule: Angle of Incidents = Angel of Reflection 5. Repeat steps 1-4 with a new line

Drawing a ray diagram for a plane mirror Rule: Angle of Incidents = Angel of Reflection 5. Repeat steps 1-4 6. Use dashed lines to continue the with a new line reflected rays back behind the mirror and draw the image where the lines meet (vertex)

Drawing a ray diagram for a plane mirror Practice drawing diagrams for plane mirrors Normal

Image Properties We describe the images mirrors produce using the acronym SPOT S: Size P: Position O: Orientation T: Type

Image Properties S: Size Is the image bigger or smaller than the object P: Position O: Orientation T: Type

Image Properties S: Size Is the image bigger or smaller than the object P: Position Is the image closer to mirror or further O: Orientation T: Type

Image Properties S: Size Is the image bigger or smaller than the object P: Position Is the image closer to mirror or further O: Orientation Is the image inverted v v or upright T: Type

Image Properties S: Size Is the image bigger or smaller than the object P: Position Is the image closer to mirror or further O: Orientation Is the image inverted v v or upright T: Type Is the image real (in front of the mirror) or virtual (behind the mirror) v v

S: Same size Image Properties for Plane Mirrors P: Same distance O: Upright T: Virtual

Drawing a ray diagram for a curved mirror Convex and concave mirror diagrams have some different parts than a plane mirror diagram Principle axis: line drawn at right angle to the centre of the mirror F/ Focal Point : Point on the principal axis, halfway between the mirror and the centre of the circle created by the mirror 2F: 2 times the focal distance, found at the centre of the circle created by the mirror Principle Axis 2F F

Drawing a ray diagram for a curved mirror Rule: Lines going into the mirror parallel to the principle axis, come out through the focal point (F) Lines going in through the focal point, come out parallel v 2F v F

Drawing a ray diagram for a convex mirror Rule: In through F out parallel, in parallel, out through F 1. Draw a ray from the object into the mirror

Drawing a ray diagram for a convex mirror Rule: In through F out parallel, in parallel, out through F 1. Draw a ray from the 2. Draw a line from F object into the mirror to the same point & continue it on past the mirror

Drawing a ray diagram for a convex mirror Rule: In through F out parallel, in parallel, out through F 1. Draw a ray from the 2. Draw a line from F 3. Draw a ray from the object object into the mirror to the same point & through the mirror as if to continue it on past go through F the mirror 4. Draw a reflected ray coming back parallel to the axis

Drawing a ray diagram for a convex mirror Rule: In through F out parallel, in parallel, out through F 5. Continue the reflected ray back behind the mirror and draw the image where the lines meet

Image Properties of Convex Mirror S: Smaller P: Closer O: Upright T: Virtual

Drawing a ray diagram for a concave mirror Rule: In through F out parallel, in parallel out through F 1. Draw a ray from the object into the mirror parallel to the principle axis v v

Drawing a ray diagram for a concave mirror Rule: In through F out parallel, in parallel out through F 1. Draw a ray from the 2. Draw a reflected ray object into the mirror from that point and parallel to the principle axis through F v v v v

Drawing a ray diagram for a concave mirror Rule: In through F out parallel, in parallel out through F 3. Draw a new ray passing through F into the mirror v v

Drawing a ray diagram for a concave mirror Rule: In through F out parallel, in parallel out through F 3. Draw a new ray passing 4. Draw a reflected ray through F into the mirror coming back parallel v v v v

Drawing a ray diagram for a concave mirror Rule: In through F out parallel, in parallel out through F 3. Draw a new ray passing 4. Draw a reflected ray 5. Draw the image where through F into the mirror coming back parallel the reflected rays cross v v v v v v

Drawing a ray diagram for a concave mirror Rule: In through F out parallel, in parallel out through F

Image Properties of Convex Mirror 1 st Example 2 nd Example v v v v For concave mirrors image properties depend on how close the object is to the mirror

Image Properties of Convex Mirror v v v v v v Behind 2F Between 2F & F In front of F S -smaller -larger -larger P -closer -further -further O -inverted -inverted -upright T -real -real -virtual

Modeling Light http://studyjams.scholastic.com/studyjams/jams/science/e nergy-light-sound/light-absorb-reflect-refract.htm