Thin Lenses

Thin Lenses

To locate the image of a diverging lens, the following three rays are drawn from the top of the object:

•Ray 1 is drawn parallel to the principal axis. After being refracted by the lens, this ray emerges directed away from the focal point on the front side of the lens.

•Ray 2 is drawn through the center of the lens and continues in a straight line.

•Ray 3 is drawn in the direction toward the focal point on the back side of the lens and emerges from the lens parallel

to the principal axis.

Thin Lenses

Thin Lenses

The Fresnel lens on the left has the same focal length as the thick lens on the right but is made of much less glass.

Thin Lenses

Combination of Thin Lenses

		Therefore, two thin lenses in
		contact with each other are
		equivalent to a single thin
		lens having a focal length
	(2.13)
		given by Equation 2.13.

Lens Aberrations

The departures of actual images from the ideal predicted by our simplified model are called aberrations.

Spherical Aberrations

Chromatic Aberrations

The Camera

The ratio f/D is called the f-number of a lens:

The Eye

The Eye

Approximate color sensitivity of the three types of cones in the retina.

The Eye

Farsightedness (or hyperopia)

The Eye

Nearsightedness (or myopia)