Optics

A.  The Optics of Mirrors

1.  Plane mirrors

a.  Flat mirrors.

b.  Make virtual images (images that have no light rays passing through them).

2.  Concave mirrors

a.  Bowl shaped mirrors.

b.  The focal point is where the reflected light rays meet.

c.  Three object source locations:

1)  Distance of object is slightly greater than focal length - reflected object is real, enlarged, and inverted.

2)  Object is at the focal point - all reflected rays are parallel to the optical axis; no image is formed (used for lights).

3)  Distance of object is less than the focal length - reflected object is virtual, enlarged, and upright.

3.  Convex mirrors

a.  Curve outward.

b.  Reflected image is always virtual, smaller, and upright.

c.  Images are closer than they appear to be.

B.  The Optics of Lenses

1.  Convex lenses

a.  Thicker in the middle than at the edges.

b.  Thicker lenses have shorter focal lengths.

c.  Three cases:

1)  Object is more than two optical lengths from lens - image is real, smaller, and inverted (human eye, camera).

2)  Object is between one and two focal lengths from lens - image is real, enlarged, and inverted (projectors).

3)  Object is less than one focal length from lens - image is virtual, enlarged, and upright (magnifying glass).

2.  Concave lenses

a.  Thinner in the middle than at the edges.

b.  Image formed is virtual, smaller, and upright.

c.  Used to make clear images of faraway objects in combination with others lenses.

3.  Human vision correction

a.  Nearsightedness (myopia)

1)  Cannot see thing far away very well.

2)  Light focuses before it hits the retina.

3)  Concave lenses correct it.

b.  Farsightedness (hyperopia)

1)  Cannot see close objects very well.

2)  Light does not focus before it hits the retina.

3)  Convex lenses correct it.

c.  Astigmatism

1)  Surface of the eye is curved unevenly.

2)  Causes blurry vision.

3)  Lenses are curved to compensate.

C.  Optical Instruments

1.  Telescopes

a.  Magnify things that are far away.

b.  Types:

1)  Refracting

a)  Uses two convex lenses.

b)  The large, objective lens gathers light.

c)  The smaller eyepiece magnifies the light.

d)  Two types:

1]  Astronomical - image is inverted.

2]  Terrestrial - an extra lens makes the image upright.

2)  Reflecting

a)  Uses a lens for an eyepiece.

b)  Uses a concave mirror as the objective to collect the light.

c)  Also uses a plane mirror to redirect the light from the mirror to the eyepiece.

2.  Microscopes magnify very small things that are very close.

3.  Cameras

a.  Gather light through a lens and project it onto light-sensitive film.

b.  Image is real, smaller, and inverted.

c.  Special lenses:

1)  Wide-angle lenses can view much wider areas.

2)  Telephoto lenses are very long and magnify an object.

D.  Applications of Light

1.  Polarized light

a.  Light whose waves can vibrate in only one plane.

b.  Eliminates glare.

2.  Lasers

a.  Light Amplification by the Stimulated Emission of Radiation.

b.  Laser light is coherent (has only one wavelength and amplitude), so it does not spread out.

c.  Very inefficient in energy usage, but useful.

1)  Cutting tools in medicine and industry.

2)  Surveying.

3)  Measuring distance.

4)  Communications (CDs).

3.  Optical fibers

a.  Fiber optics makes use of total internal reflection.

b.  Used in communication.