RIGHT PAGE 46 October 15, 2012

Focus: Light Bends and Bounces

Objective: investigate reflection and refraction

HW: article and question

Warm-Up:

How can you bend a pencil without breaking it?

Words to Know:

reflection

refraction

Word to Know: Reflection

Reflection: bouncing of light off a surface

Reflection

Reflection occurs when light bounces off objects.    If the surface is rough, the light scatters.  If the surface is smooth and flat, the light will bounce off it at equal angles. 

http://www.kidport.com/reflib/science/Light/ReflectionRefraction.htm

http://water.me.vccs.edu/courses/env211/lesson15_print.htm

Word to Know: RefractionRefraction:

light is bent as it goes through a material

The water in the glass bends light as you’re looking at it. So part of the straw looks like it’s in a different place.

Refraction

What do you see when you place a pencil in a glass of water? Why?

The pencil appears to bend where it enters the water. The pencil is not really bent. The light we see has bent as it moves from water to air. This is called refraction.

Refraction lets you see objects that are normally hidden.

Why does light go through some things and not others?  What is transparent?

Objects can be classified by how much light they transmit. There are 3 categories:TransparentTranslucentOpaque Most of the light that strikes the object will pass through it. Examples: Air, Water, Clear Glass.

Cornell Notes

What is translucent?   

What is opaque?

Some of the light that strikes the object will pass through it. Some of the light will spread out in all directions so objects aren’t as clearly seen. Examples: Lampshades, frosted glass, notepaper. No light passes through the object.Examples: Heavy fabrics, books, construction paper.

Vocabulary to Know

Exploration

• You will use shine a flashlight through each of the following objects: Plastic Wrap, Foil, Science textbook, Paper plate, Cardboard, Plastic Cup, 5 sheets of paper, 1 sheet of paper, and Plastic grocery bag.

• After using the flashlight, you will observe what happens and decide if the object is transparent, translucent or opaque based on the notes above.

• Finally, you will answer the questions on your class work/guided notes sheet using your notes, brains and observations.

Exit TicketComplete on your classwork sheet:1. When I shine a light through my object no light

passes through it. What is my object?A. TranslucentB. OpaqueC. TransparentD. Glass

2. When I shine a light through my object, some light passes through it, but some goes in different direction. What is my object?A. TranslucentB. OpaqueC. TransparentD. Glass

RIGHT PAGE 48 October 16, 2012

Focus: Light can also scatter

Objective: investigate scattering of light

HW: write a letter about today’s lesson

Warm-Up:

Why is the sky blue?

Why are clouds white?

Which material will scatter light the most?Let’s brainstorm what is scattering, predict the answer, then investigate  A.  a smooth piece of wax paper  B.  a wrinkled piece of aluminum foil  C.  a piece of dark construction paper  D.  a block of wood

What is scattering?  How does scattering affect how we see?  Why is the sky blue?

Scattering is when particles in transparent material are hit by light passing through it. The particles will scatter certain colors of ROY G BIV (visible light) so that we only see those colors.  The sky is blue because particles in the sky scatter the blue color in visible light so that it is reflected into our eyes.

Cornell Notes

LAB• PROCEDURE• Fill the container with water.• Add 10 ml (2 tsp) of milk to the water.

Put on the lid, and gently shake the container until the milk and water are mixed.

• In a dark room, shine the light at the side of the container from about 5 cm (2 in.) away.

• Observe what happens to the beam of light.

LAB

• COLLECT DATA – Answer the following questions on your note sheet.

1. Describe the appearance of the water in the beaker BEFORE adding anything to it. What does the water look like?

2. Is the water transparent, translucent or opaque?3. After adding the milk, describe the appearance of the

water. What does the water look like now? 4. What happened to the beam of light from the

flashlight? 5. Why did the light behave this way?6. How is the sky similar to milk and water?

What is Rayleigh scattering?(or why is the sky blue)

• The shorter the wavelength, the more light is scattered– blue is scattered more than red.– this is why the sky is blue and

sunsets are red. (Fig. 13.1)

Think of white light from sun as a mixture of R, G and B

Blue is scattered the most so sky looks blue when we look away from the sunFor same reason sun looks yellow (red + green)

More atmosphere allows next shortest wavelengths (green) to scatter so sunset looks red

What is Rayleigh scattering?(or why is the sky blue)

The shorter the wavelength, the more light is scattered blue is scattered more than red. this is why the sky is blue and sunsets

are red. sun looks yellow (red + green)

http://scijinks.nasa.gov/blue-sky

•Larger particles scatter red as well as blue and hence look white.

•Dust or smoke•Clouds; •Milk;

•There are many other types of scattering…

Light scattering in milk and smoke?

Practice Questions

1. What happens to a beam of light as it passes from air to water?  A.  It will move at a faster speed.  B. Light cannot pass through water.  C.  It will continue to move in a straight line  D. It will bend.

D

2. Which material will scatter light the most?  A.  a smooth piece of wax paper  B.  a wrinkled piece of aluminum foil  C.  a piece of dark construction paper  D.  a flat piece of wood

B.

Exit TicketComplete on your classwork sheet:1. Why does the sky look blue?

A. Because particles in the sky scatter dust, pollution, and airB. Because sunlight scatters particles in the sky to make dust, pollution,

and airC. Because particles in the sky scatter the sunlight into blue and indigo.D. Because particles in the sky mix to create blue and indigo as they

move around the earth.2. When does scattering occur?

A. Scattering occurs when particles in opaque materials are hit by light and reflect colors.

B. Scattering occurs when particles in transparent materials are hit by light passing through it.

C. Scattering occurs when light is scrambled up by translucent materials.

D. Scattering occurs when a translucent material turns into an opaque material.