Eyeglasses in the Classroom

• Autores: D. Huang, Wei Huang, Hsiang-chi Tseng
• Localización: The Physics Teacher, ISSN 0031-921X, Vol. 48, Nº. 1, 2010, págs. 12-13
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Optical phenomena can be divided into two categories: ray optics and wave optics. The former is also known as geometrical optics, and examples are reflection and refraction, while the latter is also known as physical opticsand includes interference and diffraction. In most textbooks, these two topics are presented in separate chapters.1To help students grasp corresponding principles, instructors often emphasize the contrast between these two categories. For example, the length scale of objects encountered by light beams is taken as an indicator to differentiate these two. When the scale is microscopic down to the wavelength at 550 nm for green light, the light shall be treated as a wave, while at a macroscopic scale start from a few mm for a tiny lens, the light shall be taken as a ray. Diffraction effects are almost always negligible in the formation of images by lens, and refraction effects can also be neglected safely in the discussions of interference. As a result, some students get the wrong impression that these two phenomena must manifest in quite different regimes. In this paper, we show that eyeglasses can be a very handy tool to demonstrate these two phenomena at the same time, working as a lens for light rays and also showing interference of light waves from reflections off the lens coating. According to a recent survey, more than 80 of college students in Taiwan are nearsighted, and eyeglasses are easily accessible in the classroom. Students are guided to observe, describe, and then provide qualitative explanations. And some of the students might take the challenge to work out quantitative calculations as exercises after class.