1. Physics for Scientists and Engineers II, Summer Semester 2009 1 Lecture 23: July 17 th 2009 Physics for Scientists and Engineers II

2. Physics for Scientists and Engineers II, Summer Semester 2009 2 The Wave under Refraction NormalIncident Ray Reflected Ray Refracted Ray Air Glass Angle of Refraction

3. Physics for Scientists and Engineers II, Summer Semester 2009 3 The Wave under Refraction Incident Ray, Reflected Ray, and Refracted ray are all in one plane.

4. Physics for Scientists and Engineers II, Summer Semester 2009 4 The Wave under Refraction NormalIncident Ray Reflected Ray Refracted Ray Air Glass Angle of Refraction

5. Physics for Scientists and Engineers II, Summer Semester 2009 5 Index of Refraction – not yet covered in class but needed for homwork. Wavelength in vacuum Wavelength in medium

6. Physics for Scientists and Engineers II, Summer Semester 2009 6 Snell’s Law of Refraction – not yet covered in class but needed for homwork. Snell’s Law of Refraction

7. Physics for Scientists and Engineers II, Summer Semester 2009 7 Huygens’s Principle (1678) All points on a given wave front are taken as point sources for the production of spherical secondary waves, called wavelets, that propagate outward through a medium with speeds characteristic of waves in that medium. After some time passed, the new position of the wave front is the surface tangent to the wavelets. Plane wave Old wave front New wave front Old wave front New wave front

8. Physics for Scientists and Engineers II, Summer Semester 2009 8 Huygens’s Principle : Reflection

9. Physics for Scientists and Engineers II, Summer Semester 2009 9 Huygens’s Principle : Refraction

10. Physics for Scientists and Engineers II, Summer Semester 2009 10 Dispersion n is a function of.

11. Physics for Scientists and Engineers II, Summer Semester 2009 11 The Prism

12. Physics for Scientists and Engineers II, Summer Semester 2009 12 The Prism

13. Physics for Scientists and Engineers II, Summer Semester 2009 13 The Prism

14. Physics for Scientists and Engineers II, Summer Semester 2009 14 Refraction and Reflection in a Sphere (e.g., drop of water) – didn’t get to it in lecture, but if you are interested, here it is…… incoming direction outgoing direction

15. Physics for Scientists and Engineers II, Summer Semester 2009 15 Angle of Deflection

16. Physics for Scientists and Engineers II, Summer Semester 2009 16 Dispersion of the angle of deflection Largest angle of return and also the most intense light in that angle region.

17. Physics for Scientists and Engineers II, Summer Semester 2009 17 How we see the rainbow Eye For lower drops red misses the eye  Lower drops look blue For higher drops blue misses the eye  Higher drops look red

18. Physics for Scientists and Engineers II, Summer Semester 2009 18 Total Internal Reflection Incident Ray

19. Physics for Scientists and Engineers II, Summer Semester 2009 19 Optical Fibers Not within the “cone of acceptance” (light falls too steep onto the fiber wall and is not Totally reflected) Total internal reflection