Reflection and Refraction of Light

Transcription

1 Name: Date: PC1222 Fundamentals of Physics II Reflection and Refraction of Light 5 Laboratory Worksheet Part A: Law of Reflection Angle of Incidence θ i Angle of Reflection θ r Data Table 1: Reflection of light. Analysis A-1: Compare the angle of incidence and the corresponding angle of reflection using percentage difference. Show your work. Question A-1: What do you conclude about the relationship between the angle of incidence and the angle of reflection? Is your conclusion consistent with the law of reflection? State your answer as qualitatively as possible. Question A-2: Compare the reflected intensity with the incident intensity. Where did the rest of the light go? What about the transmitted light? In what direction does it travel in the lens? Page 1 of 5

2 Reflection and Refraction of Light Laboratory Worksheet Page 2 of 5 Part B: Snell s Law Angle of Incidence Angle of Refraction θ 1 θ Data Table 2: Ray Incident on Flat Surface. Question B-1: Explain why the light ray is not deflected at the lens-air interface when it comes out from the curved surface. Question B-2: Is there a general trend between the angle of refraction θ 2 and the corresponding angle of incidence θ 1? Is this trend expected from the Snell s law? Explain. Analysis B-1: Using your data in Data Table 2 and Snell s law, determine the index of refraction of acrylic n. Assume the index of refraction of air is Show a sample calculation and be sure to attach a copy of the spreadsheet to your laboratory report. Hint: Excel, by default, assumes the arguments for trigonometric functions are in radians so, in order to calculate sin θ, the function you need to use is SIN(RADIANS(Angle in Degrees)). The RADIANS function converts an angle in degrees to the corresponding value in radians. n = ±

3 Reflection and Refraction of Light Laboratory Worksheet Page 3 of 5 Angle of Incidence Angle of Refraction θ 3 θ Data Table 3: Ray Incident on Curved Surface. Question B-3: Is there a general trend between the angle of refraction θ 4 and the corresponding angle of incidence θ 3? Is this trend expected from the Snell s law? Explain. Analysis B-2: Using your data in Data Table 3 and Snell s law, determine the index of refraction of acrylic n. Assume the index of refraction of air is Show a sample calculation and be sure to attach a copy of the spreadsheet to your laboratory report. n = ± Analysis B-3: Is your value of the index of refraction of acrylic n consistent to what you obtained in Analysis B-1? Compare them using percentage difference. % difference = % Question B-4: Is the law of refraction the same for light rays going in either direction between the two media? Explain.

4 Reflection and Refraction of Light Laboratory Worksheet Page 4 of 5 Part C: Dispersion of Light θ min θ max θ θ red θ blue Data Table 4 Question C-1: What colours are present in the refracted ray? (Write them in the order of minimum to maximum angle of refraction.) Question C-2: Based on your observation, is the index of refraction larger for red or blue light? Explain. Analysis C-1: Use Snell s law to calculate the index of refraction of acrylic for red light (n red ) and index of refraction for blue light (n blue ). Show your work. n red = n blue =

5 Reflection and Refraction of Light Laboratory Worksheet Page 5 of 5 Part D: Total Internal Reflection θ c,red θ c,blue Data Table 5 Analysis D-1: Calculate the critical angle for the red light using Snell s law and the index of refraction obtained in Part C. Compare the measured and theoretical values using percentage discrepancy. Show your work. θ c,red = % discrepancy = % Analysis D-2: Calculate the critical angle for the blue light using Snell s law and the index of refraction obtained in Part C. Compare the measured and theoretical values using percentage discrepancy. Show your work. θ c,blue = % discrepancy = % Question D-1: How does the brightness of the internally reflected ray change when the incident angle changes from less than θ c to greater than θ c? Explain. 6 Laboratory Report Submit a laboratory report within ONE week after your laboratory session. Important: Before leaving the laboratory, have a demonstrator initial on your data table(s)! Last updated: Wednesday 14 th January, :05pm (KHCM)