Sections 2.3-2.5Pages 197-211

Section 2.3 Pages 197 to 199

Learner Outcome

I can demonstrate the formation of images through the use of curved mirrors

Keck Observatory: Hawaii

10 m wide concave mirror

Concave mirror – has a surface that curves inward like a bowl

Parallel light rays that hit the concave mirror will reflect at a common point called the focal point.

Good for reflecting telescopes where you want to gather as much dim light as possible

If the image is far away from the focal point, the reflected rays form an upside-down image.

The closer the object gets to the focal point, the larger the image becomes.

If the object is between the focal point and the mirror, the image becomes upright and enlarged.

Page 198 for diagram

Convex mirror – surface is curved outward

Spreads out the light rays making images appear from a smaller point behind the mirror

Read page 198 and complete the activity Make your hypothesis and prediction Make sure you record your observations

accurately After you are finished, try repeating the

exercise with a convex mirror Answer the same questions, except

using a convex mirror

… demonstrate the formation of images through the use of curved mirrors?

Questions 1 to 5, page 199 Page 199

Sample Example question.

Explain how mirrors in telescopes work to enhance our knowledge of the universe?

#1. Do curved mirrors obey the law of reflection? Explain your answer.

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#2. Someone has left a shiny metal bowl outside in the sun. Which may have the potential to damage your eyes: looking at the outside of the bowl or the inside? Explain.

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#3. An object is held extremely close to a concave mirror. Describe how the image will appear. Draw a ray diagram to explain.

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#4. If you look in at a convex mirror, would your image ever appear smaller? Explain why or why not.

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#5. Describe a practical use of a convex and concave mirror.

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Section 2.4 Pages 200 to 203

Learner Outcome

I can investigate, measure and describe the refraction of light through different materials.

Light bends when it leaves the water.

When the light ray strikes a boundary where two different substances meet (the interface) at an angle, it will change direction.

Page 200

Refraction is due to changes in the speed of light.

Light slows down as it enters different mediums.

The denser the medium, the more light will slow down and the angle of refraction will be more.

Light travels slower in materials that are denser, because there are more particles.

The Law of Refraction … when light travels from one medium, to a more dense medium, the light will be bent toward the normal, and when it exits the denser medium into a less dense medium it will bend away from the normal. The new direction of light is called the angle of refraction.

Light slows down as it enters a diamond.

Why?

Answer: Density

 

Light EmissionA well-cut diamond will reflect most of the light back to the observer's eye. A poorly cut diamond will reflect only a small proportion of the light that enters it.

 

                                                                                                                                                                    Well cut diamond - most light is reflected back to

the observer.

Cut too deep; pavilion is too thick - most light is lost through the side of

the stone.

Cut too shallow; pavilion too flat - most light is lost

through the bottom of the stone.

Refraction can also occur when light travels through air at different temperatures, because warm air is less dense than cold air.

The refraction of light through air is called a mirage.

Type of behaviour

What happens to light striking a surface

Nature of surface

What else happens?

Absorption Energy Transformation

rough, dark, opaque

some light is reflected

Reflection Bounces off smooth, shiny some light is absorbed

Refraction Travels through in a new direction

different transparent medium

some light is reflected

…investigate, measure and describe the refraction of light through different materials?

Questions 1 to 4, page 203

Sample Exam Question What is the angle of refraction in a gemstone

if the incoming angle (incidence) is 45 degrees and the angle inside the gem to the NORMAL outside the gem is 150 degrees?

#1. What happens to light rays when they pass from one medium into another medium? Explain the process of refraction.

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#2. How does the type of medium affect refraction?

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#3. When would it be easier for a bear to catch a fish (river trout): as the fish swims or when it jumps in the air? Use your knowledge of how light travels in air and water to explain.

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#4. Why do objects at the bottom of an aquarium filled with water appear closer than they actually appear?

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Section 2.5 Pages 204 to 208

Learner Outcome

I can demonstrate the formation of real images, using a double convex lens, and predict the effects of changes in the lens position on the size and location of images

Concave lens is thinner in the center than at the edges.

Light is refracted away from the center of the lens.

The light rays will never meet on the other side of the lens.

Convex lens curves outward and is thicker in the middle than at the edges.

Often called a double convex lens

Light rays are reflected toward the center of the lens and meet at the focal point.

Acts as a light collector.

Forms a real image – projected

Images can be smaller or larger than the object but are upside down

See page 208 for more details on moving the

object and lens

…demonstrate the formation of real images, using a double convex lens, and predict the effects of changes in the lens position on the size and location of images?

Questions 1 to 5, Page 208

Sample Example question

Convex lensesf. Diverge lightg. Converge lighth. Reflect lighti. Separate light into colors

#1. Why are lenses useful for moving light around? ____________________________________________________________________________________________________________________________________

#2. Draw a ray diagram that shows the path light rays take through a concave lens.

#3. What kind of image is formed when an object is placed at the focal point of convex lens? ____________________________________________________________________________________________________________________________________

#4. Use Figure 2.32 on page 208 to help you.How do the bricks let light through but still

protect your privacy?______________________________________________

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#5. Suppose you wanted to examine closely the leaf of a plant. What type of lens would you choose. Would you use a lens combination? Explain.

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Questions 1, 2, 4 to 8, Page 211

The Nature of ScienceQuestions 1-3

Study for your Section 2.0 Quiz