College Physics

# Introduction to Wave Optics

College PhysicsIntroduction to Wave Optics

Figure 27.1 The colors reflected by this compact disc vary with angle and are not caused by pigments. Colors such as these are direct evidence of the wave character of light. (credit: Reggie Mathalone)

## Chapter Outline

27.1 The Wave Aspect of Light: Interference
• Discuss the wave character of light.
• Identify the changes when light enters a medium.
27.2 Huygens's Principle: Diffraction
• Discuss the propagation of transverse waves.
• Discuss Huygens’s principle.
• Explain the bending of light.
27.3 Young’s Double Slit Experiment
• Explain the phenomena of interference.
• Define constructive interference for a double slit and destructive interference for a double slit.
27.4 Multiple Slit Diffraction
• Discuss the pattern obtained from diffraction grating.
• Explain diffraction grating effects.
27.5 Single Slit Diffraction
• Discuss the single slit diffraction pattern.
27.7 Thin Film Interference
• Discuss the rainbow formation by thin films.
27.8 Polarization
• Discuss the meaning of polarization.
• Discuss the property of optical activity of certain materials.

Examine a compact disc under white light, noting the colors observed and locations of the colors. Determine if the spectra are formed by diffraction from circular lines centered at the middle of the disc and, if so, what is their spacing. If not, determine the type of spacing. Also with the CD, explore the spectra of a few light sources, such as a candle flame, incandescent bulb, halogen light, and fluorescent light. Knowing the spacing of the rows of pits in the compact disc, estimate the maximum spacing that will allow the given number of megabytes of information to be stored.

If you have ever looked at the reds, blues, and greens in a sunlit soap bubble and wondered how straw-colored soapy water could produce them, you have hit upon one of the many phenomena that can only be explained by the wave character of light (see Figure 27.2). The same is true for the colors seen in an oil slick or in the light reflected from a compact disc. These and other interesting phenomena, such as the dispersion of white light into a rainbow of colors when passed through a narrow slit, cannot be explained fully by geometric optics. In these cases, light interacts with small objects and exhibits its wave characteristics. The branch of optics that considers the behavior of light when it exhibits wave characteristics (particularly when it interacts with small objects) is called wave optics (sometimes called physical optics). It is the topic of this chapter.

Figure 27.2 These soap bubbles exhibit brilliant colors when exposed to sunlight. How are the colors produced if they are not pigments in the soap? (credit: Scott Robinson, Flickr)
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