Flat Lens (Window) n1n1 n2n2 Incident ray is displaced, but its direction is not changed. tt 11 11 If  1 is not large, and if t is small, the displacement, d, will be quite small. d

Converging Lens All rays parallel to principal axis pass through focal point F. Double Convex P.A. F A beacon in a lighthouse produces a parallel beam of light. The beacon consists of a bulb and a converging lens. Where should the bulb be placed? n lens > n outside F At F Inside F Outside F P.A. F

Converging Lens All rays parallel to principal axis pass through focal point F. Double Convex P.A. F A beacon in a lighthouse produces a parallel beam of light. The beacon consists of a bulb and a converging lens. Where should the bulb be placed? n lens > n outside F At F Inside F Outside F P.A. F F

1) Rays parallel to principal axis pass through focal point. 2) Rays through center of lens are not refracted. 3) Rays through F emerge parallel to principal axis. Converging Lens Principal Rays F F Object P.A. Image is (in this case): Real orImaginary Inverted or Upright Enlarged or Reduced

1) Rays parallel to principal axis pass through focal point. 2) Rays through center of lens are not refracted. 3) Rays through F emerge parallel to principal axis. Converging Lens Principal Rays F F Object P.A. Image is: real, inverted and enlarged (in this case). Image

1) Rays parallel to principal axis pass through focal point. 2) Rays through center of lens are not refracted. 3) Rays toward F emerge parallel to principal axis. Diverging Lens Principal Rays F F Object P.A. Image is (always true): Real or Imaginary Upright or Inverted Reduced or Enlarged

1) Rays parallel to principal axis pass through focal point. 2) Rays through center of lens are not refracted. 3) Rays toward F emerge parallel to principal axis. Diverging Lens Principal Rays F F Object P.A. Image is virtual, upright and reduced. Image

CONVEX LENS, OBJECT BEYOND 2F From the above diagram you can see that the image is (circle the correct choices): ENLARGED, SAME SIZE, or REDUCED INVERTED or ERECT REAL or VIRTUAL

CONVEX LENS, OBJECT BEYOND 2F From the above diagram you can see that the image is (circle the correct choices): ENLARGED, SAME SIZE, or REDUCED INVERTED or ERECT REAL or VIRTUAL This could be used in a camera. Big object on small film

CONVEX LENS, OBJECT AT 2F From the above diagram you can see that the image is (circle the correct choices): ENLARGED, SAME SIZE, or REDUCED INVERTED or ERECT REAL or VIRTUAL

CONVEX LENS, OBJECT AT 2F From the above diagram you can see that the image is (circle the correct choices): ENLARGED, SAME SIZE, or REDUCED INVERTED or ERECT REAL or VIRTUAL

CONVEX LENS, OBJECT BETWEEN F AND 2F From the above diagram you can see that the image is (circle the correct choices): ENLARGED, SAME SIZE, or REDUCED INVERTED or ERECT REAL or VIRTUAL

CONVEX LENS, OBJECT BETWEEN F AND 2F From the above diagram you can see that the image is (circle the correct choices): ENLARGED, SAME SIZE, or REDUCED INVERTED or ERECT REAL or VIRTUAL This could be used as a projector. Small slide on big screen

CONVEX LENS, OBJECT AT F From the above diagram you can see that the image is (circle the correct choices): ENLARGED, SAME SIZE, or REDUCED INVERTED or ERECT REAL or VIRTUAL

CONVEX LENS, OBJECT AT F From the above diagram you can see that the image is (circle the correct choices): NO IMAGE

CONVEX LENS, OBJECT BETWEEN F AND LENS From the above diagram you can see that the image is (circle the correct choices): ENLARGED, SAME SIZE, or REDUCED INVERTED or ERECT REAL or VIRTUAL

CONVEX LENS, OBJECT BETWEEN F AND LENS From the above diagram you can see that the image is (circle the correct choices): ENLARGED, SAME SIZE, or REDUCED INVERTED or ERECT REAL or VIRTUAL This is a magnifying glass

CONCAVE LENS From the above diagram you can see that the image is (circle the correct choices): ENLARGED, SAME SIZE, or REDUCED INVERTED or ERECT REAL or VIRTUAL

CONVEX LENS, OBJECT BETWEEN F AND LENS From the above diagram you can see that the image is (circle the correct choices): ENLARGED, SAME SIZE, or REDUCED INVERTED or ERECT REAL or VIRTUAL

Converging Lens Which way should you move object so image is real and diminished? (1)Closer to lens (2)Further from lens (3)Converging lens can’t create real diminished image. F F Object P.A.

Converging Lens Which way should you move object so image is real and diminished? (1)Closer to lens (2)Further from lens (3)Converging lens can’t create real diminished image. F F Object P.A.

Which way should you move object so image is real? 1)Closer to lens 2)Further from lens 3)Diverging lens can’t create real image. ACT: Diverging Lenses F F Object P.A.

Which way should you move object so image is real? 1)Closer to lens 2)Further from lens 3)Diverging lens can’t create real image. ACT: Diverging Lenses F F Object P.A.

F Focal point determined by geometry and Snell’s Law: n 1 sin(   ) = n 2 sin(   ) Fat in middle = Converging Thin in middle = Diverging Larger n 2 /n 1 = more bending, shorter focal length. n 1 = n 2 => No Bending, f = infinity Lens in water has _________ focal length! n 1 <n 2

P.A. F Focal point determined by geometry and Snell’s Law: n 1 sin(   ) = n 2 sin(   ) Fat in middle = Converging Thin in middle = Diverging Larger n 2 /n 1 = more bending, shorter focal length. n 1 = n 2 => No Bending, f = infinity Lens in water has larger focal length! n 1 <n 2

1) Rays parallel to principal axis pass through focal point. 2) Rays through center of lens are not refracted. 3) Rays through F emerge parallel to principal axis. Assumptions: monochromatic light incident on a thin lens. rays are all “near” the principal axis. Converging Lens Principal Rays F F Object P.A. Image is real, inverted and enlarged Image

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. How much of the image appears on the screen?

Java 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.

Still see entire image (but dimmer)!

Lens Equation F F Object P.A. dodo didi f Image d o = distance object is from lens: Positive: object __________ lens Negative: object __________ lens d i = distance image is from lens: Positive: ________ image (behind lens) Negative: ________ image (in front of lens) f = focal length lens: Positive: ___________ lens Negative: ___________ lens d i = m =

Lens Equation F F Object P.A. dodo didi f Image d o = distance object is from lens: Positive: object in front of lens Negative: object behind lens d i = distance image is from lens: Positive: real image (behind lens) Negative: virtual image (in front of lens) f = focal length lens: Positive: converging lens Negative: diverging lens

Multiple Lenses Image from lens 1 becomes object for lens 2 1 f1f1 f2f2 2 Complete the Rays!!

Multiple Lenses: Magnification f1f1 f2f2 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 12 Net magnification: m net = m 1 m 2