# Physlet® Physics 3E: Optics

## Chapter 32: Electromagnetic (EM) Waves

Electromagnetic waves (also called electromagnetic radiation) are waves that obey Maxwell's equations. One of the consequences of Maxwell's equations is that there are electromagnetic waves that propagate at 3 x 108 m/s in a vacuum. This is precisely the speed of light in a vacuum! Therefore, all light-visible light, ultraviolet radiation, radio waves, microwaves, x-rays, gamma rays, and infrared radiation-is an electromagnetic wave. The difference between these waves is simply in the frequency (f ) or wavelength (λ). Since the frequency times the wavelength (f λ) is equal to the speed of propagation (which for light in a vacuum must be 3 x 108 m/s), if you know the frequency, you know the wavelength. This chapter examines propagating electric and magnetic fields and links them to the observable properties of light.

## Chapter 33: Mirrors

A mirror is an optical element that reflects the light incident on it. This chapter deals with various mirrors (flat, concave, and convex) and their properties. The focus of this chapter is understanding images formed by mirrors. You will use ray diagrams, explore the focal length and focal point of mirrors, and learn about real and virtual images in order to understand image formation, image location and image properties.

## Chapter 34: Refraction

As light changes from one medium to another, it can speed up or or slow down depending on the two media. This change in speed causes the wavelength of light to change. It can also change the direction of travel for the light. This "bending" of light is known as refraction. This chapter deals with a number of aspects of refraction including perceived images, effect on a lens, change in wavelength, and critical angle for total internal reflection.

## Chapter 35: Lenses

A lens is essentially a medium with a different index of refraction than the surrounding medium. The shape and index of refraction of the lens determine its properties. The key to designing optical systems is understanding the image formed by a given lens or combination of lenses. In this chapter many of the concepts of image formation are similar to those for spherical mirrors. The problems you will encounter will use ray diagrams to explore image formation, determine focal points, and develop methods for understanding multiple-lens systems.

## Chapter 36: Optical Applications

In this chapter we study geometrical optics as applied to real systems. A basic understanding of ideas from previous chapters, such as lens operation is, of course, assumed. Applications covered include the eye, camera, microscope, telescope, and laser cavities. Study of these applications provides a way to reinforce concepts previously learned as well as demonstrate practical uses of those concepts.

## Chapter 37: Interference

Because light is a wave, the light from two or more sources can interfere to yield distinctive patterns. The different colors of a bit of oil in a water puddle is an example of an interference effect. In this chapter, you will explore the interference of light from multiple sources using a virtual ripple tank in order to make the connection between path length difference and interference. You will also explore the interference of light incident on thin films.

## Chapter 38: Diffraction

Diffraction is the result of interference when a wave passes through an opening or edge. Diffraction effects are easier or harder to see depending on the wavelength of the wave and the size of a given opening. The physical principle behind diffraction is the same as that of interference (see Chapter 37): the superposition of waves. In order to observe the effects of diffraction, slits or gratings must be of a size comparable to the wavelength of the light.

## Chapter 39: Polarization

The polarization state of a traveling electromagnetic wave describes the orientation of the electric field over time. Both linearly and circularly polarized light are included in this chapter, which focuses on making the connection between the individual fields that comprise a traveling wave and the resultant electric field.

## Optics Appendix: What's Behind the Curtain?

Previous chapters have covered mirrors and lenses. In this appendix, mirrors and lenses are considered by asking questions regarding the optical element(s) present in the animation. The optical elements are all unknown since they are hidden behind red curtains. You are given a type of source (object, beam, point) and must analyze the resulting light rays to determine what's behind the curtain.

Overview TOC