1. Warm Up
A concave mirror has a focal length of 5 cm. If an object is 2 cm away from the mirror, where is the image?
A convex mirror has a focal length of 10 cm. A person looks at their eyeball in the mirror 8 cm away. Where is the image?

2. Optics: Reflection, Refraction Lenses
05/25/2006
Optics:
Lenses
Lecture 16

3. Analogy…
Mirrors make images with reflection
Lenses make images with refraction!

4. Remember….
Virtual images are located where reflected light appears to converge
Real images are located where reflected light actually converges

5. Convex Lenses Thicker in the center than edges.
Two focii (one on either side)
Lens that converges (brings together) light rays.
Light traveling is refracted through lens, then refracted again back into air
Any ray traveling parallel
Will be refracted through
focal point

6. Convex Lenses Lens that converges (brings together) light rays.
Forms real images and virtual images depending on position of the object
The Magnifier

7. Lens Ray Diagram Rules
Three Rays:
Ray goes parallel, refracted through f (on other side)
Ray goes through f (on same side), gets refracted parallel (on other side)
Ray goes through the center of lens

8. Concave Lenses
Lenses that are thicker at the edges and thinner in the center.
Diverges light rays
All images are right side up and reduced.
The De-Magnifier

10. How You See
Near Sighted – Eyeball is too long and image focuses in front of the retina
Near Sightedness – Concave lenses expand focal length
Far Sighted – Eyeball is too short so image is focused behind the retina.
Far Sightedness – Convex lens shortens the focal length.

11. Optics: Reflection, Refraction
05/25/2006
Cameras, in brief
pinhole
image at
film plane
object
In a pinhole camera, the hole is so small that light hitting any particular point
on the film plane must have come from a particular direction outside the camera
image at
film plane
object
lens
In a camera with a lens, the same applies: that a point on the film plane
more-or-less corresponds to a direction outside the camera. Lenses have
the important advantage of collecting more light than the pinhole admits
Lecture 16