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!
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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 - PowerPoint PPT Presentation
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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!
Review
Mirrors Definitions, Types Magnification
Mirror equation
Remember the sign conventions! (Table 23.1)
Ray tracing Images formed by
refraction Magnification
Object-Image
Concave
Convex
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
Thin 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
Converging lenses
Diverging lenses
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
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
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
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
Ray Diagram for Converging Lens, p > f
The image is real The image is inverted
Ray Diagram for Converging Lens, p < f
The image is virtual The image is upright
Ray Diagram for Diverging Lens
The image is virtual The image is upright
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.
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 F2 are 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?