Visible Light Sources of visible light: The sun Stars Lightning 2-14-13 Visible Light Sources of visible light: The sun Stars Light bulbs Fire/flame Lightning Fireflies Laser pointers

An object is “seen” only when an object emits or reflects light to the eye. luminous Objects that generate their own light. Ex: illuminated Objects that are capable of reflecting light to our eyes. Ex:

Speed of Light Q: Does light travel faster through a solid, liquid or a gas? H: Light waves travel fastest through a _____ because_____.

Demonstration

Explanation: Light travels the fastest through a gas (actually empty space) because there are less particles to move through and slow it down.

Reflection 2-13-14 Reflection – the bouncing of a light wave off a surface. Law of Reflection - the angle of reflection is equal to the angle of incidence

Regular Reflection Light waves reflect by the same angle. Diffuse Reflection Light waves reflect at many different angles.

Laser Reflection Activity Purpose: Compare reflection of visible light on different surfaces. 1. smooth 2. rough 3. shiny 4. dull

DO NOT SHINE LASER POINTERS NEAR ANYONE’S FACE – CAN CAUSE EYE DAMAGE

Reflection of Laser Pointer Data Table: Reflection of Laser Pointer Surface (ex: table, poster, curtains) Surface Type (smooth, rough, dull, or shiny) Reflection Type (regular or diffuse) 1. 2. 3. 4. 5. 6. 7. 8. 9.

Conclusion: Which types of surfaces had a regular reflection? (Answer these questions in the RAP format. Restate, Answer, Prove. Use information from your data table for the prove part.) Which types of surfaces had a regular reflection? Which types of surfaces had a diffused reflection? Ex: Smooth surfaces and shiny surfaces have a regular reflection. I could see the reflection from the laser pointer when I shined it on a soda can and the clock. Dull and rough surfaces have a diffused reflection. There was no visible reflection off of a towel and a piece of paper when I shined the laser pointer at them.

Why does the pencil appear broken? 2-14-14 Refraction Diagram: Why does the pencil appear broken?

Refraction - the bending of light when light waves speed up or slow down as they pass through different substances

The more dense a substance is, the slower light travels through it.

Refraction Picture Contest With a partner you will take pictures of light refracting. You will submit ONE for the contest. Your goal is to take the COOLEST most CREATIVE picture possible that demonstrates refraction! It MUST be a picture that YOU or your partner have taken! We will vote on the best picture on Wednesday, February 19th in class Email the picture to Mrs. Schneider by Tuesday night by 10:01 pm. Make sure both of your names on mentioned in the email. aschneider@lindberghschools.ws For Full Credit – take an accurate picture of refraction and email it on time. Two extra credit points for the winners!

Behavior of Light Three Ways Light Behaves: Reflects (Reflection) 2-25-13 Three Ways Light Behaves: Reflects (Reflection) Absorbs (Absorption) – the transfer of light energy to particles of matter Ex: light becoming dim Transmits (Transmission) – the passing of light through matter -includes refraction (light bending) Ex: light passing through glass or water

How is Light behaving? Ex 1. How does light behave when sun rays shine at a window? -Light transmits through the window, reflects off of the window, and is absorbed into the window. Ex 2. How does light behave when you shine a flash light at a towel or a blanket? -Light is absorbed into the blanket, and reflects off the blanket at different angles (diffuse reflection)

Three Different Materials: Transparent – a material that allows almost all the light to pass through and forms a clear image Ex: Translucent – a material that allows most light to pass through and forms a blurry image 3. Opaque – a material that light cannot pass through