Chapter 25: Geometric Optics

Converging lens

a convex lens in which light rays that enter it parallel to its axis converge at a single point on the opposite side

Converging Mirror

a concave mirror in which light rays that strike it parallel to its axis converge at one or more points along the axis

Corner Reflector

an object consisting of two mutually perpendicular reflecting surfaces, so that the light that enters is reflected back exactly parallel to the direction from which it came

Critical Angle

incident angle that produces an angle of refraction of 90º

Dispersion

spreading of white light into its full spectrum of wavelengths

Diverging lens

a concave lens in which light rays that enter it parallel to its axis bend away (diverge) from its axis

Diverging mirror

a convex mirror in which light rays that strike it parallel to its axis bend away (diverge) from its axis

Fiber optics

transmission of light down fibers of plastic or glass, applying the principle of total internal reflection

focal length

distance from the center of a lens or curved mirror to its focal point

focal point

for a converging lens or mirror, the point at which converging light rays cross; for a diverging lens or mirror, the point from which diverging light rays appear to originate

geometric optics

part of optics dealing with the ray aspect of light

index of refraction

for a material, the ratio of the speed of light in vacuum to that in the material

law of reflection

angle of reflection equals the angle of incidence

magnification

ratio of image height to object height

mirror

smooth surface that reflects light at specific angles, forming an image of the person or object in front of it

power

inverse of focal length

rainbow

dispersion of sunlight into a continuous distribution of colors according to wavelength, produced by the refraction and reflection of sunlight by water droplets in the sky

ray

straight line that originates at some point

real image

image that can be projected

refraction

changing of a light ray’s direction when it passes through variations in matter

virtual image

image that cannot be projected

zircon

natural gemstone with a large index of refraction

speed of light in a vacuum

the maximum speed at which light travels in empty space, approximately 299,792 kilometers per second (km/s)

Snell’s Law

a principle that relates the angle of incidence and the angle of refraction when light passes between different media, defined by the equation n1 sin(θ1) = n2 sin(θ2).

Thin lens equations

formulas that describe the relationship between the object distance, image distance, and focal length of a thin lens, including the equation ( \frac{1}{f} = \frac{1}{do} + \frac{1}{di} ).

Image length

half the radius of curvature.The distance from the lens to the image formed by the lens.