Module 16: Light Rays

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Introduction

Light is something we can all see, but what is it really? It is not at all obvious that light is an electromagnetic wave and there is much that we can learn about it without knowing this fact. However, knowing that it is a wave (and, in fact a transverse wave) makes it easier to explain many of its interesting properties.

Learning Objectives

Upon completion of this module, students will be able to:

  • Define what a light ray is.
  • Draw ray diagrams.
  • Describe why light bends as it goes from one medium to another.
  • Calculate to find the light's resultant path.
  • Define dispersion.
  • Explain how white light can be split up into components by dispersion.
  • Explain the principles of lenses.
  • Use ray diagrams to find images.
  • Explain the proof that light is a wave.
  • Describe the physics of light mixing.

To Do List

1. Watch the Video Lectures (links below)
2. Complete the Practice Problems (links below)
3. Take the Module 16 Quiz
4. Complete the Exam Practice Problems for Module 16
5. Complete the Practice Exams 3

Video Lectures and Practice Problems 

Lesson 16.1 Ray Optics and Mirrors

We use the fact that light travels in straight lines to understand a pinhole camera and basic mirror phenomena.

Lesson 16.2 Refraction 

Here we cover everything to do with refraction - the bending of light as it moves from one medium to another. This is done quantitavely   (Snell's Law), and the critical angle for internal reflection is found. In addition we learn other effects of light in the atmosphere, including mirages (caused by refraction), and rainbows (caused by dispersion).

Lesson 16.3 Lenses

Lenses are a long topic in many physics courses, but here we stress the fundamentals, why lenses focus the light and how the lens in our eye is vital.

Lesson 16.4 Light Wave Interference

Light travels as a wave, and the proof that light is a wave is interference. We look at how to observe interference from two light waves.

Lesson 16.5 Polarization 

Polarization is direct proof that a light wave is transverse. Here we look at several examples, one of which has a particularly surprising result.

Lesson 16.6 Light Mixing

We all know about mixing of color paints, but that is not mixing of differently colored light. Here we look at how light from different parts of the spectrum can be added to make white light, and discuss what is means for an object to have color.

Quiz

Once you have watched the lectures and completed the practice problems, you should demonstrate your understanding by taking the Module 16 Quiz. Be sure to submit the quiz before its deadline.

End-of-Course Survey

We ask you to take this End-of-Course Survey. Your feedback will help us evaluate the course and make it better for the future.

Coming Up

Exam 3 is coming up next! The exam will cover Modules 1 though 16, mainly focusing on Modules 11-16. To prepare, you should complete the Exam 3 Review.