Artifacts in Nuclear Medicine with Identifying and resolving artifacts.
Lect19 handout
1. Physics 102: Lecture 19 Lenses and your EYE Ciliary Muscles
2. 3 Cases for Converging Lenses Image Object Upright Enlarged Virtual Inside F Image Object Inverted Enlarged Real Between F & 2F Object Image Inverted Reduced Real Past 2F
3. Only 1 Case for Diverging Lenses F F Object P.A. Image is always virtual, upright, and reduced . Image
4. Preflight 19.1 A converging lens is used to project a real image onto a screen. A piece of black tape is then placed over the upper half of the lens.
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6. Multiple Lenses Image from lens 1 becomes object for lens 2 1 f 1 f 2 2 Lens 1 creates a real, inverted and enlarged image of the object. Lens 2 creates a real, inverted and reduced image of the image from lens 1. The combination gives a real, upright, enlarged image of the object. Example
7. Multiple Lenses: Image 1 f 1 f 2 First find image from lens 1. f 2 = 5 cm Example 1 2 d o = 15 cm f 1 = 10 cm d i = 30 cm
8. Multiple Lenses: Image 2 f 1 f 2 Now find image from lens 2. d o = 15 cm f 1 = 10 cm d i = 30 cm L = 42 cm Notice that d o could be negative for second lens! 1 2 Example f 2 = 5 cm d o =12 cm d i = 8.6 cm
9. Multiple Lenses: Magnification f 1 f 2 d o = 15 cm f 1 = 10 cm d i = 30 cm f 2 = 5 cm L = 42 cm d o =12 cm d i = 8.6 cm 1 2 Example Net magnification: m net = m 1 m 2
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11. ACT: Focusing and the Eye Cornea n= 1.38 Lens n = 1.4 Vitreous n = 1.33 Which part of the eye does most of the light bending? 1) Lens 2) Cornea 3) Retina 4) Cones Ciliary Muscles
12. Eye (Relaxed) 25 mm Determine the focal length of your eye when looking at an object far away. Example Object is far away: Want image at retina:
13. Eye (Tensed) 25 mm Determine the focal length of your eye when looking at an object up close (25 cm). 250 mm Example Object is up close: Want image at retina:
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15. Preflight 19.3 1) 13 cm 2) 26 cm 3) 52 cm A person with normal vision (near point at 26 cm) is standing in front of a plane mirror. What is the closest distance to the mirror where the person can stand and still see himself in focus?
16. If you are nearsighted... Want to have (virtual) image of distant object, d o = , at the far point, d i = -d far . (far point is too close) Example Too far for near-sighted eye to focus d far Near-sighted eye can focus on this! Contacts form virtual image at far point – becomes object for eye. d o f lens = - d far
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18. If you are farsighted... When object is at d o , lens must create an (virtual) image at -d near Want the near point to be at d o . (near point is too far) Example Too close for far-sighted eye to focus Far-sighted eye can focus on this! d o Contacts form virtual image at near point – becomes object for eye. d near
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23. Magnifying Glass Magnifying glass produces virtual image behind object, allowing you to bring object to a closer d o : and larger ′ Compare to unaided eye: : Ratio of the two angles is the angular magnification M: object virtual image h i h o d i d o magnifying glass
24. Angular Magnification M = d near /d 0 = d near /f +1 For max. magnification, put image at d near : so set d i = -d near : object virtual image h i h o d o magnifying glass (d near = near point distance from eye.) d i Smaller f means larger magnification For the lens : 1 d o 1 d i 1 f 1 d o 1 f 1 d i
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Editor's Notes
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Demo 71
Just like for mirrors If d 0 larger, d i is smaller, |m| smaller If d 0 smaller, d i is larger, |m| larger
Numbers in red are for a digital camera Macula/fovea is super sensitive part only sees about 15 degrees http://hyperphysics.phy-astr.gsu.edu/hbase/vision/retina.html#c2
25 mm ~ 1 inch
Tensed means more curvature, more bending, shorter focal length
My eyes: 6.5 diopters, implies f=-0.15 m (my far point is 0.15 m, or 6”, or 15 cm) Big # means smaller f, more bending (worse eyesight)
My near point with far correction: 65 cm Want near point at 25 cm Need 1/f=1/.25-1/.65 1/f=2.5 diopters
