PHYS 101 1st Edition Lecture 26 Outline of Last Lecture I. Electromagnetic Waves Outline of Current Lecture II. Electromagnetic Waves continued…III. Deriving Refractive Index IV. Practice ProblemsCurrent LectureII. Electromagnetic Waves continued…A. When light (or EM-wave) enters a material, its speed changes, its wavelength also changes, but its frequency does not change. III. Deriving Refractive Index N = c/v ; where n is refractive index, c is the speed of light in the vacuum and v is the speed of light in the material. Prove that n = in vac/air/materialSo 1n: in vac/air = c/f c = (in vac/air )(f)In the material max = v/f v= (max)(f)n= c/v = (in vac/air f)/ (max f) The f’s cancel, leaving n = in vac/air / max.IV. Practice Problems #11. A laser beam is incident from air at an angle of 30 degrees to the vertical onto a solution of corn syrup in water. If the beam is reflected to 19.24 degrees to the vertical… A) n2= ? These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.n1sin1 = n2sin2 ; where n1 is air and n2 is syrup 1 sin (30) = n2 sin (19.24) n2 = 1.52If in vac/air = 632.8 X 10-9 m B) syrup = ? n = in vac/air / syrup1.52 = 632.8 X 10-9 / syrup syrup = 416 X 10-9 mC) frequency in syrup but we who came to class are smart & know that fsyrup= fvac/airSo, let us calculate fvac/air vac/air = c/f 632.8 X 10-9 m = 3 X 108 / f f = 4.74 X 1014 Hz D) V in syrup N = C/V 1.52 = 3 X 108 / V V = 1.97 X 108 m/s ~2 X 108 m/s compare to C (3 X 108 m/s) #11. n1sin1 = n2sin2 ; where n1 is air and n2 is water. Remember that n1= 1 and n2=1.333 (given on exam). 1 sin1 = 1.333 sin(45)sin1 = 1.333/21 = sin-1(1.333/2)1 = 70.5 degrees (from vertical) from the horizontal, = 90-70.5 = 19.5
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