light ray, light ray a cruise through the wonderful world of reflection and refraction (aka...
TRANSCRIPT
![Page 1: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/1.jpg)
Light Ray, Light Ray
A Cruise Through the Wonderful World of Reflection and Refraction
(aka Geometric optics)
No Light, No Sight
Presentation Text ©2001 Philip M. Dauber
![Page 2: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/2.jpg)
What is Light?
• Electromagnetic Radiation with wavelength
(visible) 400 to 700 nm (nanometers) or 4x10-7 to 7x10-7 meters
• Travels in straight lines
• Bounces (reflects) off certain materials
• Refracts (bends) in transparent materials
• Travels at c = 3 x 108 m/sec (in vacuum)
![Page 3: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/3.jpg)
Reflection
• Light bounces off objects
• Consider “rays” – light moving in straight line
• Law of reflection: angle of incidence = angle of reflection
![Page 4: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/4.jpg)
Law of Reflection
![Page 5: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/5.jpg)
Law of Reflection i = r
• I - incident ray
• R - reflected ray
• N – normal
• Theta-I is angle of
incidence
• Theta –R is angle of
reflection
![Page 6: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/6.jpg)
Types of Reflection
![Page 7: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/7.jpg)
How Plane Mirror Forms Image
![Page 8: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/8.jpg)
Image From Plane Mirror
• Virtual
• Behind mirror
• Right side up(upright)
• Left-right reversed
• Located equal
Distance behind mirror
• Same size as object
![Page 9: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/9.jpg)
Distance RelationshipImage is as far behind mirror as object is in
front
![Page 10: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/10.jpg)
How Curved Mirror Forms Real Images
![Page 11: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/11.jpg)
How Law of Reflection Leads to Images from Spherical Mirror
• C is center of
curvature
• F is focal point
• Real image will
be located on same side
of mirror as object
![Page 12: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/12.jpg)
Rules of Reflection – Two “Special” Rays
• An incident ray parallel to principal axis will pass through the focal point after reflection.
• An incident ray passing through the focal point will leave mirror parallel to principal axis
![Page 13: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/13.jpg)
What’s So “Special?” About Special Rays?
• Its easy to predict where they will go
• Use Law of Reflection
![Page 14: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/14.jpg)
Ray Diagram – Object Beyond C = 2f
• Real image
• Inverted
• Smaller than object
• Note use of two
“special” rays
• What is another?
![Page 15: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/15.jpg)
Ray Diagram – Object at C = 2f or between f and 2f
• Image inverted• Located at 2f • Same size as object
• Image inverted• Further than 2f• Larger than object
![Page 16: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/16.jpg)
Object at 2f
![Page 17: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/17.jpg)
Object Between f and 2f
![Page 18: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/18.jpg)
Object Closer to Mirror Than f “Shaving Mirror” Case
• Image virtual
• Behind mirror
• Upright
• Larger than object
![Page 19: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/19.jpg)
Object at f
• Must use different ray (goes to intersection of principal axis and mirror)
• No image formed
![Page 20: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/20.jpg)
Object Closer to Mirror Than F
![Page 21: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/21.jpg)
Mirror Equation
• f is positive for concave mirror
Question: Where will image formed by a lens with 20 cm focal length be if object is placed 30 cm from mirror?
![Page 22: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/22.jpg)
How Big is The Image?
• M is magnification
• - sign means image is inverted
Question: If the object in the question on previous slide is 2 cm high, how high is image?
![Page 23: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/23.jpg)
Convex (Diverging) Mirrors
• f is negative
• Light rays spread,
not focused; images virtual
• 7-11 mirror foils
thieves
![Page 24: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/24.jpg)
Ray Diagram for Convex Mirror
• One ray parallel to p.a.
• Second ray heads for
focus behind mirror
• Diverging rays must be
extended behind mirror
(dotted lines)
• Image virtual, upright, smaller
![Page 25: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/25.jpg)
Why Are Some Rearview Mirrors Convex?
![Page 26: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/26.jpg)
Problem
• A 1.6 m tall thief stands 10m away from a 7-11 mirror with 2m (negative) focal length.
Where is the image and how tall is it?• Use
• Note: negative di means image behind mirror
![Page 27: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/27.jpg)
Index of Refraction
• Light slows down in transparent materials other than vacuum(like car slows in sand)
• v = c/n velocity of light in medium
• n is called index of refraction
• n = about 1.5 for glass
• n = 1.33 for water
![Page 28: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/28.jpg)
Index of Refraction
• Ratio of speed of light in vacuum to speed of light in material
• n = c/v = 3.0 x 108 m/s/v• n always greater than one
![Page 29: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/29.jpg)
Refraction: How Much Does It Bend?
• Angle of incidence i
• Angle of refraction r
• Snell’s Law:
ni sin i = nr sin r
![Page 30: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/30.jpg)
Helpful Analogy:The Band of Sand
• What happens when the car drives into the sand?
highway sand
Which way does the car turn?
![Page 31: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/31.jpg)
Toward and Away from Normal
• When light enters a more dense (greater n) medium, it bends toward the normal
• When light enters a less dense (smaller n) medium, it bends away from the normal
![Page 32: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/32.jpg)
Mysteries?
• Why do a person’s legs appear shorter when they are standing in water?
• Why Does A Glass Rod Disappear in Mineral Oil?
![Page 33: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/33.jpg)
Problem
• Light strikes a flat piece of glass(n = 1.5) at 60 degrees to the normal. What is the angle of the light in the glass?
i = 60o
r
![Page 34: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/34.jpg)
Solution
• ni sin i = nr sin r
• ni = 1 nr = 1.5
sin r = 1.00/1.50 sin i = 0.577
r = 35.2o
![Page 35: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/35.jpg)
Critical Angle• Light ray leaves more dense medium
• Angle of refraction approaches 900
• Past critical angle there is no refracted ray
![Page 36: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/36.jpg)
Critical AngleThe angle of incidence past which there is no
refracted ray
• ni sin i = nr sin r
• sin c = nr/ni sin900 = nr/ni
• If ray emerges into air• sin c = 1/ni
c
![Page 37: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/37.jpg)
Example
• What is the critical angle for light rays leaving a swimming pool? What does the world look like to a swimmer at the bottom of the pool?
Sin c = 1.00/1.33 = 0.750
c = 490
Swimmer sees outside world compressed into a circle whose edge makes a 49 degree angle to the vertical
![Page 38: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/38.jpg)
Total Internal Reflection
![Page 39: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/39.jpg)
Applications of TIR
• Prisms in Binoculars, Periscopes
![Page 40: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/40.jpg)
Dispersion• Separation of white light into spectrum of
wavelengths (colors)
![Page 41: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/41.jpg)
Why Dispersion Occurs
• Index of refraction, n, depends on wavelength
• Typically n decreases as increases
• Exit angle from prism depends on
White light
![Page 42: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/42.jpg)
Forming a Rainbow
![Page 43: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/43.jpg)
Fiber Optics
• Fiber Optic Amplifier Module
Spy under door optics
endoscopePhotos courtesy JDS Uniphase Inc.
![Page 44: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/44.jpg)
Lenses
• Lenses can focus or diverge light
• Act like tiny prisms
![Page 45: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/45.jpg)
Thin Lens
• Convex lenses have two focal points
![Page 46: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/46.jpg)
Focal Length of Lens
• That distance, f, from lens at which parallel rays are brought to a point
• Power of a lens:
P = 1/f
• Unit is “diopter” (m-1)
• Used by optometrists
Focal point
![Page 47: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/47.jpg)
Three Special, Predictable Rays
• Avoid application of Snell’s Law
• Parallel to principal axis, exiting rays goes through far focus
• Through near side focus; exiting ray parallel
• Through center of lens (no refraction)
![Page 48: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/48.jpg)
Object Distance Greater than 2f
• Image real
• Inverted
• Smaller
• Opposite side
from object
• Like camera
![Page 49: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/49.jpg)
Object at 2f or between f and 2f
• Image same size, real• At 2f
• Image larger, real• Greater than 2f• Like projector
![Page 50: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/50.jpg)
Diverging Lens – Does NOT focus
• Image virtual
• Upright
• Smaller
• Same side
as object
• Closer than f
![Page 51: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/51.jpg)
Thin Lens Equation
• F positive for converging lens, negative for diverging lens
• di positive for real images, negative for virtual images (same side)
![Page 52: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/52.jpg)
Magnification
• Relates image and object height to image and object distance
![Page 53: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/53.jpg)
Solving Lens Problems
• Read and re-read problem• Draw ray diagram with 2 or 3 special rays• Solve lens and magnification equations for
unknowns• Follow sign conventions including
– f positive for converging lenses– f negative for diverging lenses– di negative on same side of lens as object
![Page 54: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/54.jpg)
Lens Problem
• A fly one cm tall is 30 cm from a lens with a focal length of 20cm. Where is the (real) image of the fly located and how tall is it?
1/di = 1/f – 1/d0 = 1/20 – 1/30 = 3/60 – 2/60 = 1/60
di = 60 cm on other side of lens from fly
hi = -h0 di/d0 = -2cm
- sign means image inverted
![Page 55: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/55.jpg)
Object Inside of f – Magnifying Glass
• Image virtual
• Upright
• Same side as object,
behind object
• larger
![Page 56: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/56.jpg)
Problem
• An object is placed 10 cm from a 15cm focal length converging lens. Where is the image?
1/di = 1/f – 1/d0 = 1/15 – 1/10 = -1/30
di = -30 cm
- sign means image is virtual and n same side of lens as object
![Page 57: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/57.jpg)
Object at f
• No image formed
![Page 58: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/58.jpg)
Diverging Lens Problems
• Remember, f is negative
• di will also be negative
![Page 59: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/59.jpg)
Problem
• Where must a small insect be placed if a 25 cm diverging lens is to form a virtual image 20 cm in front of the lens?
1/d0 = 1/f – 1/di = -1/25 + 1/20 =
(-4+5)/100 = 1/100
d0 = 100 cm in front of lens
![Page 60: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/60.jpg)
Combinations of Lenses and Lenses with Mirrors
• The image produced by the first element becomes the object of the second
• Two converging lenses with focal lengths 20.0 and 25.0 cm respectively are placed 80.0 cm apart. An object is placed 60 cm in front of the first lens. Where is the image?
![Page 61: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/61.jpg)
Lenses and Mirrors
• Sketch a ray diagram of a set up in which a mirror and a lens work together
• Find out how an astronomical telescope works– Refracting– Reflecting
• Find out how a simple compound (two lens) microscope works
![Page 62: Light Ray, Light Ray A Cruise Through the Wonderful World of Reflection and Refraction (aka Geometric optics) No Light, No Sight Presentation Text ©2001](https://reader030.vdocuments.site/reader030/viewer/2022032607/56649ec65503460f94bd1976/html5/thumbnails/62.jpg)
Acknowledgements
• Graphics and animation courtesy of Tom Henderson, Glenbrook South High School, Illinois
• Photos of fiber optic components courtesy of JDS Uniphase, Inc