17-2-applications-of-diffraction-interference-and-coherence_summary

The section 17.2 of the text discusses the applications of wave concepts related to diffraction, interference, and coherence in the context of light. The key learning objectives are explaining the behaviors of waves, performing calculations related to wave applications, and understanding the role of wave characteristics and behaviors in medical and industrial applications. Terms introduced in the section include: - Laser: a device that produces intense, directional, and narrow beams of coherent light, typically used in surgery, reading CDs, barcode scanning, industrial cutting, and in space exploration for distance measurements. - Diffraction grating: a device for dispersing light into its spectral components, consisting of a large number of evenly spaced parallel slits, used in spectroscopy, holography, and as a novelty item. - Resolution: the ability to distinguish two points or objects as separate, in the context of wave interference, it refers to the limit at which two wave sources cannot be resolved due to the diffraction effect. The concept of coherent light is also emphasized, noting that it is a stream of photons with the same energy and phase, typically produced using Einstein's idea of stimulated emission of radiation (laser). The section explains how the limit of resolution is related to Heisenberg's uncertainty principle, and emphasizes that perfect resolution is impossible due to the wave nature of light. Common examples of lasers and diffraction gratings mentioned include surgical lasers, lasers used in reading CDs, diffraction gratings on CDs, and iridescent minerals, feathers, and butterflies. The chapter also discusses the role of diffraction gratings in spectroscopy, where they are used to separate different wavelengths of light, and in the analysis of light emitted by biological and medical samples. Diffraction gratings are preferred over two slits due to their sharper and brighter bands. The section also provides a Snap Lab activity for exploring diffraction gratings using a CD and sunlight, and a Fun In Physics activity discussing the structure and operation of CDs as diffraction gratings. The section concludes with a discussion of how diffraction limits the resolution of images, particularly in telescopes and microscopes. The section also presents equations for calculating the angle of constructive interference for a diffraction grating, as well as the diffraction limit to resolution based on Lord Rayleigh's criterion.