- An is a lens or mirror.
- An is the apparent reproduction of an object, formed by an optical element (or collection of them) reflecting and/or refracting light.
- Images can either be (same orientation as object) or (upside-down with respect to object).
- The optical axis is a line that passes through the optical element perpendicular to it
- The point where the optical axis meets the optical element is called the .
- The of a lens is where the lens is thickest (for a converging lens) or thinnest (for a diverging lens).
- The of a mirror is the center of curvature.
- Image and object distances are measured along the optical axis.
- Signs are relative to the path of the light.
- If the object is on the same side as the incoming light, then , otherwise .
- If the image is on the same side as the outgoing light, then , otherwise .
- For a lens, the incoming and outgoing sides are different (light goes through a lens).
- For a mirror, the incoming and outgoing sides are the same (light bounces off a mirror).
- Focal lengths are also signed. If the element tends to incoming parallel light (a or a ), then the focal length is negative. If the element incoming parallel light ( or ), the focal length is positive.
Principles for Unit II
This unit in particular has a lot of terminology. To help you stay focused, the principles (where we will begin analyzing situations) are:
How light interacts with surfaces and materials
- Law of reflection which is best understood in the particle picture.
- Law of refraction which is best understood in the wave picture.
- Light slows when it enters a medium, but the energy of a photon cannot change. So the wavelength must!
Optical elements and ray diagrams
- The position of the image formed by an optical system is located at where:
- is the object distance, using the sign conventions used above.
- is the image distance, using the sign conventions used above.
- is the focal length with its correct sign.
- For ray diagrams: one ray in parallel and out through focal point, one ray in through focal point and out parallel, one ray using the center of the system.
- And point where photons seem to emerge can be used as an object. Such a point could be a real source of photons (an object) or an image from another optical element.
A lens or a mirror
The apparent reproduction of an object, formed by an optical element (or collection of them) reflecting and/or refracting light.
When the image is the same orientation as the object
When the image is upside-down with respect to the object.
The point where the optical axis meets the optical element.
For a lens, where the lens is thickest.
For a mirror, the center is the center of curvature.
Spread the light rays apart.
a concave lens in which light rays that enter it parallel to its axis bend away (diverge) from its axis
A mirror that bends away from the light source (
Bring light rays to a point.
a convex lens in which light rays that enter it parallel to its axis converge at a single point on the opposite side
A mirror that bends towards the incoming light )