Lenses

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 (Converging)

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.

Summary for Convex Lens

When 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

di    -   virtual image

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 (Diverging) Lens

Object

Image

Summary for Concave (Diverging) Lens

Always:

virtual, reduced, upright image

Notice!

The art of drawing ray diagrams has not changed drastically.

The equations for image formation in LENSES are the same as the equations for image formation in MIRRORS.