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Announcements HW set 9 due this week; covers Ch 23 and Ch 24.1-4 Office hours:

Announcements HW set 9 due this week; covers Ch 23 and Ch 24.1-4 Office hours: Prof Kumar ’ s Tea and Cookies 5 – 6 pm today My office hours Th 2 -3 pm or make an appointment Come to class April 19 course and instructor evaluation 8 bonus HITT points

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Announcements HW set 9 due this week; covers Ch 23 and Ch 24.1-4 Office hours:

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  1. Announcements • HW set 9 due this week; covers Ch 23 and Ch 24.1-4 • Office hours: • Prof Kumar’s Tea and Cookies 5 – 6 pm today • My office hours Th 2 -3 pm • or make an appointment • Come to class April 19 • course and instructor evaluation • 8 bonus HITT points • Always check out http://www.phys.ufl.edu/courses/phy2054/spring11/ for more announcements • QUESTIONS? PLEASE ASK!

  2. Concave Review • Mirrors • Definitions, Types • Magnification • Mirror equation • Remember the sign conventions! (Table 23.1) • Ray tracing • Images formed by refraction • Magnification • Object-Image Convex

  3. Atmospheric Refraction and Mirages • A mirage can be observed when the air above the ground is warmer than the air at higher elevations • The rays in path B are directed toward the ground and then bent by refraction • Related to total internal reflection – n is smaller near the ground • The observer sees both an upright and an inverted image

  4. Thin Lenses Converging lenses • Thin lens - consists of a piece of glass or plastic • refracting surfaces are either spherical or planar • distance between the surface of the lens and the center of the lens is negligible • converging lenses • positive focal lengths • thickest in the middle • diverging lenses • negative focal lengths • thickest at the edges Diverging lenses

  5. Focal Length of Lenses • focal length, ƒ -image distance that corresponds to an infinite object distance • same as mirrors • thin lens has two focal points, corresponding to parallel rays from the left and from the right Converging lenses Diverging lenses

  6. Lens Equations • The geometric derivation of the equations is very similar to that of mirrors • The equations can be used for both converging and diverging lenses • converging lens has a positive focal length • diverging lens has a negative focal length

  7. Focal Length for a Lens • The focal length of a lens is related to the curvature of its front and back surfaces and the index of refraction of the material the lens maker’s equation

  8. Ray Diagrams for Thin Lenses • Three rays are drawn • The first ray is drawn parallel to the first principle axis and then passes through (or appears to come from) one of the focal lengths • The second ray is drawn through the center of the lens and continues in a straight line • The third ray is drawn from the other focal point and emerges from the lens parallel to the principle axis • There are an infinite number of rays, these are convenient

  9. Ray Diagram for Converging Lens, p > f • The image is real • The image is inverted

  10. Ray Diagram for Converging Lens, p < f • The image is virtual • The image is upright

  11. Ray Diagram for Diverging Lens • The image is virtual • The image is upright

  12. Problem 23.36, p 786 • The nickel’s image in the figure has twice the diameter of the nickel when the lens is 2.84 cm from the nickel. Determine the focal length of the lens.

  13. Problem 23.59, p 788 • The figure shows a converging lens with radii R1 = 9 cm and R2 = 11 cm, in front of a concave spherical mirror of radius 8 cm. (a) If the focal points F1 and F2are 5 cm from the vertex of the thin lens, what is the index of refraction of the lens? (b) If the lens and the mirror are 20 cm apart and an object is placed 8 cm to the left of the lens, what is the position of the final image and its magnification as seen by the eye in the figure? (c) Is the final image real or inverted?

  14. Answer to 23.36

  15. Answer to 23.59

  16. Answer to 23.59 (cont’d)

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