PHYSICS02-11_12-Quarter4-1004-PF-FD.pptx

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1. General Physics 2 Science, Technology, Engineering, and Mathematics Lesson 10.4 Law of Refraction

2. ‹#› Is the light really crooked in this photo?

3. ‹#› Is the branch in this photo really broken?

4. ‹#› Do not let your eyes deceive you. Those are just the applications of refraction. In this lesson, we will discuss how light refract.

5. ‹#› Why does light refract?

6. ‹#› Apply Snell’s Law (STEM-GP12OPTIVb-15). Explain the conditions for total internal reflection (STEM-GP12OPTIVb-14).

7. ‹#› Solve problems involving reflection and refraction in contexts such as, but not limited to (polarizing) sunglasses, atmospheric rainbows, and haloes. (STEM-GP12OPTIVb-21).

8. ‹#› Infer how the refractive index affects the optical density of a material. Explain how light refracts. State Snell’s law.

9. ‹#› Determine the conditions of total internal reflection. Solve problems related to the refraction and total internal reflection of light. Identify applications of refraction and total internal reflection in daily life.

10. ‹#› Light is refracted when it travels at a particular angle ( θ b ) into a medium or substance that has a different refractive index, as shown. Refraction

11. ‹#› Refractive index (n) or index of refraction refers to the ratio of the speed of light in free space to that of its speed in a given medium. A material’s refractive index is determined by its optical density , or the “inert tendency” of a material’s molecules to keep the absorbed energy of an EM wave in the form of oscillating electrons before releasing it back as a new disturbance. Refractive Index

12. ‹#› It may also be understood as the measure of the bending of the light ray as it travels from one medium to another. This is given by: Refractive Index

13. ‹#› Common Refractive Indices Material Refractive Index (n) vacuum 1.0000 air 1.0003 ice 1.31 water 1.333 ethyl alcohol 1.36 plexiglass 1.51 crown glass 1.52

14. ‹#› Material Refractive Index (n) light flint glass 1.58 dense flint glass 1.66 zircon 1.923 diamond 2.417 rutile 2.907 Gallium phosphide 3.50 germanium 4.01-4.05 light flint glass 1.58 Common Refractive Indices

15. ‹#› How does a material’s refractive index affect its optical density?

16. ‹#› Optical density must not be confused with mass density (mass per unit volume). The more optically dense an object is, the slower that a wave will travel through that material.

17. ‹#› How does reflection and refraction differ? Refraction of Light

18. ‹#› Snell’s law (or the Law of Refraction) describes the relationship between the angle of incidence θ a and angle of refraction θ b as light passes through two different media. Snell’s Law

19. ‹#› Mathematically, it states that the ratio of the sines of the angle of incidence θ a and angle of refraction θ b (considering both are measured relative to the normal to the surface) is equivalent to the inverse ratio of the two indices of refraction. Snell’s Law

20. ‹#› Applications of Snell’s Law Snell’s Law

21. ‹#› Total Internal Reflection

22. ‹#› Total internal reflection happens when a light ray from a material (a) is incident (or forms an angle of incidence) on a second material (b) with a refractive index smaller than that of a, such that n b > n a .

23. ‹#› Under what conditions does total internal reflection occurs?

24. ‹#› The speed of light as it passes through an unknown material is measured at 2.13 ✕ 10 8 m/s. Determine the material’s index of refraction.

25. ‹#› The speed of light as it passes through an unknown material is measured at 2.13 ✕ 10 8 m/s. Determine the material’s index of refraction. The refractive index of the unknown material is 1.40. This is the refractive index of a fluoropolymer.

26. ‹#› ‹#› A light ray has a speed of 1.99 ✕ 10 8 m/s as it passes through another unknown medium. What is the material’s index of refraction?

27. ‹#› A laser beam travelling in air pierces through ethyl alcohol at an angle of incidence of 25.15 o . Determine the angle of refraction.

28. ‹#› A laser beam travelling in air pierces through ethyl alcohol at an angle of incidence of 25.15 o . Determine the angle of refraction. The angle of refraction is 18.22 o .

29. ‹#› ‹#› Light initially beamed on air hits a plexiglass at an incidence angle of 40 o . What angle of refraction will result from this interaction?

30. ‹#› An incident ray strikes surface AB of a glass prism in the figure that has a 1.52 index of refraction. Determine the (a) critical angle and (b) the largest value that α may have without any light refracted out at the surface AC of the prism if the prism is immersed in air.

31. ‹#› An incident ray strikes surface AB of a glass prism in the figure that has a 1.52 index of refraction. Determine the (a) critical angle and (b) the largest value that α may have without any light refracted out at the surface AC of the prism if the prism is immersed in air? The critical angle is 41.13 o . The largest possible value of α is 48.86 o .

32. ‹#› ‹#› Suppose the prism on the previous example is now submerged in water. Solve for the (a) critical angle and the (b) largest possible of α if total internal reflection will occur on Surface AC as a light ray strikes it.

33. ‹#› Identify what is being referred to in each of the following statements. Light is refracted when it travels at a particular angle into a material that has a ____________________ refractive index. The refractive index refers to the ratio of the speed of light in ____________________ to that of its speed in ____________________. Free space has a refractive index of ____________________.

34. ‹#› Identify the refractive index of each of the following media. Medium Refractive Index Speed of Light in the medium cubic zirconia _________________ 1.39 ✕ 10 8 m/s crown glass _________________ 1.97 ✕ 10 8 m/s quartz _________________ 1.95 ✕ 10 8 m/s

35. ‹#› Refraction refers to the bending of light at a certain angle θ b when it passes through a different medium. The refractive index ( n ) or index of refraction refers to the ratio of the speed of light in free space to that of its speed in a given medium.

36. A material’s refractive index is determined by its optical density , or the “sluggish tendency” of a material’s molecules to keep the absorbed energy of an EM wave in the form of oscillating electrons before releasing it back as a new disturbance. Snell’s law (or the Law of Refraction) describes the relationship between the angle of incidence θ a and angle of refraction θ b as light passes through two different media. ‹#›

37. A light ray passing through a material with a larger refractive index bends toward the normal to the surface. The opposite holds true. A ray oriented along the normal will not bend, regardless of the composition of the medium. ‹#›

38. Total internal reflection happens when a light ray from a material (a) is incident (or forms an angle of incidence) on a second material (b) with a refractive index smaller than that of a , such that n b > n a . ‹#›

39. ‹#› Concept Formula Description Snell’s Law of Refraction where n is the material’s refractive index (either object a or b); c is the speed of light in free space, and v is the speed of light through the material. Use this formula to solve for the refractive index of a material.

40. ‹#› Concept Formula Description Refractive Index/ Index of Refraction where n is the material’s refractive index, and θ is the angle of incidence (a) or refraction (b) from the normal to the surface. Use this relationship to derive the formulas for the unknown values related to Snell’s law.

41. ‹#› Concept Formula Description Total Internal Reflection where θ crit is the critical angle for total internal reflection; n b is the index of refraction of the second material, and n a is the index of refraction of the first material. Use this formula to solve for the critical angle when the conditions of TIR are observed.

42. ‹#› ‹#› Can reflection and refraction occur at the same time from a single interface? Justify your answer.

43. ‹#› Faughn, Jerry S. and Raymond A. Serway. Serway’s College Physics (7th ed) . Singapore: Brooks/Cole, 2006. Giancoli, Douglas C. Physics Principles with Applications (7th ed). USA: Pearson Education, 2014. Halliday, David, Robert Resnick and Kenneth Krane. Fundamentals of Physics (5th ed) . USA: Wiley, 2002. Knight, Randall D. Physics for Scientists and Engineers: A Strategic Approach (4th ed) . USA: Pearson Education, 2017. Serway, Raymond A. and John W. Jewett, Jr. Physics for Scientists and Engineers with Modern Physics (9th ed) . USA: Brooks/Cole, 2014. Walker, James S. Physics (5th ed) . USA: Pearson Education, 2017. Young, Hugh D., Roger A. Freedman, and A. Lewis Ford. Sears and Zemansky’s University Physics with Modern Physics (13th ed) . USA: Pearson Education, 2012.