PHY2049: Chapters 33/341What is Light?Î1. Something made of rays that travel on straight lines So-called geometric optics Subjects of Chapters 33/34Î2. Wave So-called wave optics Subjects of Chapters 35 and 36Î3. Electromagnetic waveÎ4. Made of photons So-called quantum optics Needed to understand the laser and interactions between light and matter More approximationWave-particle dualityPHY2049: Chapters 33/342CHECKPOINTLight travels from a medium whose index of refraction is n1into another medium whose index of refraction n2. In which of the two cases is n2larger than n1?(b)(a)Case aPHY2049: Chapters 33/343White lightPrisms have double reflections and limited resolution. To study a light spectrum, diffraction gratings (see Chapter 36) are used instead of prisms. See a demo in the lobby.redvioletChromatic dispersionPHY2049: Chapters 33/344n2n1For a total reflection to occur, n1 has to be larger than n2.Total Internal ReflectionPHY2049: Chapters 33/345QuizA point source of light is located 3 m below the body of water. Find the diameter of the circle at the surface through which light emerges from the water.θ = 48.8° 2r= 6.84 mradiusn2 ≈ 1n1 = 1.33PHY2049: Chapters 33/346All reflected rays extrapolate to point I, as if they all originated there. The viewer perceives a virtual image located at I. Convention: use negative sign for virtual image. Turns out to be very useful.i = –pPlain mirrorPHY2049: Chapters 33/347QuizhA six-foot-tall gator stands in front of a mirror on a wall. In order for him to see his reflection in the mirror from top to toe, what is the minimum height required of the mirror?3 ft.6
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