Unit 12: Behavior of Light: Reflection, Refraction, Diffraction, Interference
Unit Menu
Chapter 29
Lessons 1 - Reflection and Refraction
1.1Quick Lab – Images, Images and More Images!
1.2Web Walk – Law of Reflection
1.3Web Walk – Reflections and Curved Mirrors
1.4Lab Simulation – Reflections in a Plane Mirror
1.5Web Walk – Refraction, Snell's Law, and Internal Reflection
1.6Lab Simulation – Snell's Law
1.7Lesson Wrap Up – Quiz – Reflection and Refraction
Chapter 30
Lesson 2 - Lenses - To Diverge or to Converge
2.1Web Walk – Converging and Diverging Lenses
2.2Quick Lab – A Lensless Lens!
2.3Lab Activity – Images, Images and a Convex Lens!
Knowledge Check
2.5Lesson Wrap Up – Quiz - Lenses
Chapter 31
Lesson 3 - Diffraction and Interference
3.1Web Walk – Interference and Wave Behavior
3.2Quick Lab – Rainbows, Bubbles & More!
Lesson 4 - Unit Wrap Up – Behavior of Light Exam
Learning Goals
By the end of this unit, you will be able to:
* distinguish between regular and diffuse reflection of light
* state the law of reflection (law of mirrors)
* distinguish between real and virtual images
* describe the characteristics of an image produced by a plane mirror
* draw ray diagrams showing how an image is produced by a plane mirror
* identify a curved mirror as converging (concave) or diverging (convex)
* for plane and curved mirrors, identify any of the following on appropriate diagrams:
incident ray
reflected ray
angle of incidence
angle of reflection
normal
principal axis
center of curvature
principal focus (focal point)
focal length
* describe the characteristics of images produced by converging and diverging mirrors
* conduct an experiment to determine the focal length of a concave mirror
* draw accurate ray diagrams for both concave and convex mirrors to show how an image is produced
* use the mirror formulas to locate and describe the image formed by convex and concave mirrors
* describe some of the uses of plane and curved mirrors
* define index of refraction
* solve problems using Snell's law, involving:
index of refraction
angle of incidence
angle of refraction
* define critical angle and total internal reflection
* describe total internal reflection, its effects, and its applications
* solve problems involving total internal reflection
* identify a lens as converging (convex) or diverging (concave)
* for lenses, identify any of the following from an appropriate diagram:
incident ray
normal
refracted ray
angle of incidence
angle of refraction
principal axis
principal focus (focal point)
focal length
* conduct an experiment to determine the focal length of a convex lens
* draw accurate ray diagrams for both convex and concave lenses to show how an image is produced
* describe the characteristics of images produced by converging and diverging lenses
* use the lens formulas to locate and describe the image formed by convex and concave lenses
* describe the effects of aberration in lenses
* give examples of common devices that refract light
* describe and give examples of common applications of the following wave phenomena
reflection
refraction
diffraction
interference (superposition principle)
Doppler shift
scattering (dispersion)
* explain the causes of bright and dark interference bands (fringes) of light
* describe and compare single slit interference with double slit interference patterns
* describe the causes of visible diffraction of waves
* describe the properties of laser light
Check it out!
As members of The Students Alert for Physics Principles (SAPP) your mission is the help others understand the behavior of light – so they can have a reflective experience. Reflection, refraction, interference and diffraction are phenomena that are not always easily understood by the person wanting to connect to the world of the physics and the behavior of light. The SAPP is listed as the featured speaker/s at the Physics Wannabees Conference in Des Moines , Iowa . Your topic to discuss is “She comes in colors everywhere!” Remember - there is more to the behavior of light than meets to eye!
There is more to the behavior of light than meets the eye! Most people associate reflection with mirrors, rainbows with rain showers, mirages with roadways, refraction with lenses, glass, and water, and prisms with the separating the colors of light. A common misconception is that light only travels in a straight line. When light encounters a different substance, its path will change. The behavior of light during reflection, refraction, diffraction, and interference will be studied during this unit. Questions to consider while studying this unit include: How do lenses and mirrors work? How do “light pipes” work? What is a mirage? As light and matter interact, light can be reflected, refracted, diffracted, transmitted, absorbed, dispersed, polarized and experience interference. Through the course of this unit, you will look at each of these interactions. The nature of light and its effects should become more meaningful to you once you understand their importance.
Lesson 1: Reflection and Refraction
“If you can't see my mirrors, I can't see you!” Where have you seen this statement? Right! – On the back of trucks ahead of you on the interstate. Reflections are interesting. Reflections of reflections are fascinating. Reflections of reflections of reflections … are kaleidoscopes! There are places in the world where, in late afternoon and early evening, mountains can be seen rising out of the horizon on the ocean. The mountains are real, but they are too distant to be seen normally. The question that probably comes to mind is – Why is this? How is this possible? Other questions to ponder are: What causes “ghosting” of distant objects in double-walled windows? Why is your image in a spoon upside down if you look into the bowl, but right side up if you look at the back? Why do you see better underwater when you wear goggles? After completing this lesson, you will be able to explain these phenomena!
12.1.1 Quick Lab – Images, Images and More Images!
Problem: How does reflected light travel to your eyes?
Procedure:
A. Set a mirror in the middle of a sheet of paper and support it at the edges either by holding the mirror or using a small piece of clay. Place the pencils in the rubber stoppers and stand one of the pencils about 5 cm in front of the mirror. Looking at the image of the pencil in the mirror, place the second pencil behind the mirror where the image of the first pencil appears to be. If you have located the image correctly, the image of the first pencil and the second pencil itself will remain “together” as you move your head from side to side. Draw a line along the front edge of the mirror and mark the position of the pencils. Remove the pencils and the mirror from the paper. Measure the distance (d o ) from the object (the first pencil) to the mirror and the distance (d i ) of the image (second pencil) to the mirror. Draw the path you think the light takes from the first pencil to your eye as you observe the image.
B. Set two mirrors on edge on a protractor at a right angle to each other (Use clay to support them). Place a coin or a map pin between the two mirrors. Count the images produced. Keeping the map pin between the mirrors, reduce the angle to 72 o and count the images produced. Reduce the angle by 5 o at a time, and count the number of images that form at each angle. Prepare a table to record the data collected.
Analysis:
1. How did the distance (do) from the first pencil to the mirror compare with the distance (di) of the image to the mirror?
2. What happens to the number of images when you decrease the angle between the two mirrors?
3. Explain the reason for the multiple images you have observed.
4. Using the information that you have gained, explain the construction and the operation of a kaleidoscope.
Conclusion: What have you learned?
12.1.2 Web Walk – Law of Reflection aka: Law of Mirrors
Go to (The Physics Classroom – High School Physics Tutorial) Lesson 1: Reflection and Its Importance “The Role of Light to Sight”. Complete the lesson noting the diagrams and the bold red terms.
Click NEXT to go to “The Line of Sight”. Complete the lesson noting the diagrams, the bold terms and complete the Check Your Understanding.
Click NEXT to go to “The Law of Reflection”. Complete the lesson noting the diagrams, the bold terms, view the animation, and complete the Check Your Understanding. What is the law of reflection?
Click NEXT to go to “Specular and Diffuse Reflection”. Complete the lesson noting the diagrams, the bold terms and complete the Check Your Understanding. How are the types of reflections different?
Click Go to Lesson 2 (Image Formation in Plane Mirrors). Complete “Why Is An Image Formed?” noting the diagrams, the bold terms, and the animations.
Click NEXT to go to “Image Characteristics”. Complete the lesson noting the diagrams, the bold terms, and complete the Check Your Understanding. What is a virtual image?
Click NEXT to go to “Ray Diagrams”. Complete the lesson noting the diagrams, the bold terms, and complete the Check Your Understanding. What is the fundamental rule is followed when constructing ray diagrams?
Click NEXT to go to “What Portion of a Mirror is Required?”. Complete the lesson noting the diagrams and complete the Check Your Understanding.
Click NEXT to go to “Right Angle Mirrors”. Complete the lesson noting the diagrams and the bold terms.
Click NEXT to go to “Other Multiple Mirror Systems”. Complete the lesson noting the diagrams, the italics terms, and complete the Check Your Understanding.
Analysis:
Consider the following questions and submit your responses to your notebook.
1. State the law of reflection?
2. What are the characteristics of a virtual image?
3. What is a ray diagram?
4. For a reflection in a plane mirror, how does the object size and object distance compare to the image size and image distance?
5. Why does a plane mirror appear to reverse images left to right, but not top to bottom?
12.1.3 Web Walk – Reflections and Curved Mirrors
Go to Physics Classroom – High School Physics Tutorial) Lesson 3: Concave Mirrors, “The Anatomy of a Curved Mirror”. Complete the lesson noting the diagrams, the bold red terms, and complete Check Your Understanding.
Click NEXT to go to “Reflection of Light and Image Formation”. Complete the lesson noting the diagrams, the bold terms and the animations.
Click NEXT to go to “Two Rules of Reflection for Concave Mirrors”. Complete the lesson noting the diagrams and guidelines for reflected light rays. What are the guidelines for constructing a ray diagram?
Click NEXT to go to “Ray Diagrams – Concave Mirrors”. Complete the lesson noting the diagrams, the bold red terms, the animations and complete Check Your Understanding. What are the guidelines for constructing a ray diagram?
Click NEXT to go to “Image Characteristics for Concave Mirrors”. Complete the lesson noting the diagrams, the bold red terms, the case examples and complete Check Your Understanding.
Click NEXT to go to “The Mirror Equation”. Complete the lesson noting the equations and the sample problems. Complete the Check Your Understanding. What are the mirror equations?
Click NEXT to go to “Spherical Aberration”. Complete the lesson noting the diagrams. How can spherical aberration be corrected?
Go to Physics Classroom – High School Physics Tutorial) Lesson 4: Convex Mirrors, “Reflection and Image Formation for Convex Mirrors”. Complete the lesson noting the diagrams and the rules of reflection for convex mirrors.
Click NEXT to go to “Ray Diagrams – Convex Mirrors”. Complete the lesson noting the diagrams and examples. Do the practice ray diagrams.
Click NEXT to go to “Image Characteristics for Convex Mirrors”. Complete the lesson noting the diagrams and complete the Check Your Understanding.
Click NEXT to go to “The Mirror Equation – Convex Mirrors”. Complete the lesson noting the equations and the sample problems. Complete the Check Your Understanding. What are the mirror equations? Are they the same for concave mirrors?
12.1.4 Lab Simulation – Reflections in a Plane Mirror
Mirrors: Plane and Not so Simple
Analysis:
Consider the following questions and submit your responses to your notebook.
1. What are the guidelines for constructing a ray diagram?
2. What are the mirror equations?
3. What is spherical aberration and how can it be corrected?
4. Compare and contrast the characteristics of virtual and real images in terms of orientation, location (position) relative to the mirror, size, and if it can be projected on a screen.
5. This statement “Objects may be closer than they appear.” is on the right hand outside mirror of your car. What is the significance of this warning?
12.1.5 Quick Lab – Refraction of Light
Go to online.cctt.org/physicslab/content/Phy1/lessonnotes/refractionoflight/refraction.asp (Online Physics Lab) Read and take notes.
Go to
12.1.6 Web Walk – Refraction, Snell's Law, and Internal Reflection
Go to (The Physics Classroom – High School Physics Tutorial) Lesson 1: Refraction at a Boundary “Boundary Behavior”. Complete the reading noting the diagrams and the animation.
Click NEXT to go to “Refraction and Sight”. Complete the reading noting the diagrams, the bold terms and view the animation.
Click NEXT to go to “Cause of Refraction”. Complete the activity noting the diagrams (analogies) and view the animation.
Click NEXT to go to “Optical Density and light Speed”. Complete the reading noting the diagrams and table of indices of refraction. What is the relationship between optical density and index of refraction? How is the index of refraction determined?
Click NEXT to go to “The Direction of Bending”. Complete the reading noting the diagrams, the red bolded terms, the practice problem, and compete the Check Your Understanding. What is the “Least Time Principle”?
Click NEXT to go to “The Secret of the Archer Fish”. Complete the reading noting the diagrams. What is the secret of the Archer Fish?
Click Go to Lesson 2 (The Mathematics of Refraction). Complete “The Angle of Refraction” noting the diagrams and the bold red terms.
Click NEXT to go to “Snell's Law”. Complete the activity noting the diagrams, the bold red terms, and the two example problems. Write a statement for Snell's Law.
Click NEXT to go to “Ray Tracing and Problem Solving”. Complete the activity noting the diagrams, the bold terms, the example problems, and complete the Check Your Understanding. Write the equation for Snell's Law.
Click NEXT to go to “Determination of n Values”. Complete the activity noting the diagrams, the bold terms, the sample data from a lab, and complete the Check Your Understanding.
Click Go to Lesson 3 (Total Internal Reflection). Complete “Boundary Behavior Revisited” noting the diagrams and the bold red terms.
Click NEXT to go to “Total Internal Reflection”. Complete the activity noting the diagrams, the bold red terms, and complete Check Your Understanding. Define critical angle.
Click NEXT to go to “The Critical Angle”. Complete the activity noting the diagrams, the bold terms, the example problems, and complete the Check Your Understanding. How would you calculate critical angle?
Analysis:
Consider the following questions and submit your responses to your notebook.
1. How is the index of refraction determined?
2. What is the secret of the Archer Fish?
3. Write a statement for Snell's Law. Write the equation for Snell's Law.
4. What is total internal reflection (TIR)?
5. Define critical angle. How would you calculate critical angle?
Knowledge Check
Now that you have an understanding of the law of reflection, consider this practical application of it. Some department store display windows are slanted inward at the bottom. The purpose of this is to reduce the glare (reflection) from brightly illuminated buildings across the street, which would make it difficult for shoppers to see the display. Prepare a sketch, to be shared and submitted to your instructor, of light rays reflecting from such a window to show how this technique works.
12.1.7 Quiz – Reflection and Refraction
Lesson 2: Lenses – To Diverge or to Converge!
Our view of the world of the world has been widened due to the discovery of lenses. When light shines through a lens, there is a bending of light as it enters and leaves glass or some other material. The light is refracted due to the shape and material of the lens and forms images of the object being viewed. The images formed can appear smaller, larger, closer, farther, upright, or inverted of the object being viewed. During this lesson you will apply the concept of refraction to lenses and pin holes. Some questions to ponder include: Why are there round, sometimes elliptical spots of light called sunballs beneath the trees on a sunny day? Why do you see better underwater when you wear goggles – after all it is not a lens?