LensesPhysics

Mrs. Coyle

What phenomenon is evident in lenses?

https://wiki.brown.edu/confluence/display/PhysicsLabs/PHYS+0080+BC

Basic Types of Lenses

• Convex

• Concave

Convex Lens

http://www.shokabo.co.jp/sp_e/optical/labo/lens/lens.htm

Concave Lens

http://www.shokabo.co.jp/sp_e/optical/labo/lens/lens.htm

Type of Image

• Real or Virtual

• Enlarged or Reduced

• Erect or Inverted

Convex Lens

Center C

f

Ray Diagram for Convex Lens

Principal Axis

http://facstaff.gpc.edu/~pgore/PhysicalScience/ray_diagram_sample.jpg

Rules for Ray Diagrams for Convex Lens

• A parallel ray refracts through the focal point.

• A ray through the center of the lens continues straight.

• A ray coming through the focal point, refracts parallel to the principal axis.

• http://higheredbcs.wiley.com/legacy/college/halliday/0471320005/simulations6e/index.htm?newwindow=true

Summary for Convex LensWhen the object is:• Beyond 2F

• At 2F

• Between 2F and F

• At F

• Between F and lens

Then the image is:

• Between 2F and F

• At 2F

• Beyond 2F

• No image

• Virtual image

Sign Convention

do  +    object distance

di   +   real image, other side of lens

di    -   virtual image, same side as object

hi + erect image

hi - inverted image

f     +   converging lens (convex) f     -    diverging lens (concave)

Magnification

M = hi = -di

ho do

Note: When magnification is <0, the image is inverted.

Lens Equation

1 = 1 + 1

f do di

Concave Lens

Object

Image

Summary for Concave Lens

Always:

• Virtual, reduced, upright image

• http://bcs.wiley.com/he-bcs/Books?action=resource&bcsId=1074&itemId=0471320005&resourceId=169