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Unformatted text preview: Physics 212
Lecture 26: Lenses
Lenses Physics 212 Lecture 26, Slide 1 Music
Who is the Artist?
E) Ramblin’ Jack Elliott
U. Utah Phillips Why?
Last time I had to talk about
“circles & arrows”
45th anniversary of Arlo being
arrested for litterin after Thanksgiving
See the movie !!
Physics 212 Lecture 26, Slide 2 Your Comments
“Focal length. Also, do we have homework over
Focal Homework 13 is now up: Due Nov 30 break? Or ever again from this point?”
“Can you please put the preparation excersises up soon?”
“Can you explain the terms upstream and downstream?” Exam 3 Prep has been up for weeks..
See course homepage Refers to position relative to lens
Light flows from upstream to downstream “What is the point of having a virtual image if you
can not see it?”
can “how does the index of refraction affect the
focal YOU CAN !!
Just look in the mirror
Index of refraction determines how
much light “bends”
40 “I would like to discuss how we haven't had a
country music lecture yet..”
Does Arlo count??
Does Arlo count?? 30
20 “Bacon. How come you put up peoples comments
about not putting their comments up, but you have
NEVER spoken on bacon?”
0 05 Confused Confident Physics 212 Lecture 26, Slide 3 Refraction
n1sin(θ1) = n2sin(θ2)
θ2 That’s all of the physics –
everything else is just geometry! Physics 212 Lecture 26, Slide 4 Object Location
• Light rays from sun bounce off object and go in all
– Some hits your eyes We know object’s location
by where rays come from. We will discuss eyes in lecture 28… Physics 212 Lecture 26, Slide 5 Waves from object are focused by lens Physics 212 Lecture 26, Slide 6 Two Different Types of Lenses Physics 212 Lecture 26, Slide 7 Converging Lens: Consider the case where the shape of the lens is
such that light rays parallel to the axis of the mirror are all
“focused” to a common spot a distance f behind the lens:
to f f
Physics 212 Lecture 26, Slide 8 Recipe for finding image:
1) Draw ray parallel to axis refracted ray goes through focus
2) Draw ray through center refracted ray is symmetric object f
image You now know the position of the same point on the image
Physics 212 Lecture 26, Slide 9 S > 2f image is:
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- Spring '11