Geometric and Wave Optics Flashcards

These vocabulary flashcards cover key terms and formulas for Geometric and Wave Optics as presented in the lecture notes for Chapters 25 and 27.

Ray

A simple line used to show the path light takes, modeling the straight-line travel of light.

Law of Reflection

The principle stating that the angle of incidence ($\theta_i$) is equal to the angle of reflection ($\theta_r$), both measured from the normal line.

Normal

An imaginary line perpendicular to a surface used as a reference for measuring angles of incidence and reflection.

Virtual Image

An image that looks like it is behind a mirror or on the same side as the object in a lens, but where light does not actually go; it cannot be projected onto a screen.

Corner Reflectors

Devices using two mirrors meeting at a right angle that send the outgoing ray parallel to the incoming ray.

Refraction

The bending of light when it enters a different material because the speed of light changes.

Index of Refraction ($n$)

A value that compares the speed of light in a vacuum ($c = 3.00 \times 10^8\,m/s$) to its speed in a specific material ($v$), defined by the formula $n = \frac{c}{v}$.

Snell’s Law

The formula $n_1 \sin(\theta_1) = n_2 \sin(\theta_2)$ which determines how much light bends when moving from one material to another.

Dispersion

The phenomenon where white light spreads out into different wavelengths (colors) because the index of refraction depends on the wavelength.

Total Internal Reflection (TIR)

A phenomenon where light is completely reflected back inside a material with a higher index ($n_1 > n_2$) when the incident angle is greater than the critical angle.

Critical Angle ($\theta_c$)

The incident angle at which the refracted angle is $90^\circ$, calculated using $\theta_c = \sin^{-1}(\frac{n_2}{n_1})$.

Fiber Optics

Systems that use total internal reflection to keep light pulses traveling inside a fiber for communication or medical endoscopes.

Converging Lens

A convex lens that bends parallel rays toward the central axis so they meet at a focal point on the opposite side.

Diverging Lens

A concave lens that bends parallel rays away from the central axis, creating a focal point by tracing the rays backward.

Lens Power ($P$)

The reciprocal of the focal length, calculated by $P = \frac{1}{f}$, where $f$ is in meters and power is measured in diopters ($D = m^{-1}$).

Real Image

An image formed when refracted rays actually meet; it has a positive image distance ($d_i$), can be projected onto a screen, and is inverted.

Thin Lens Equation

The relationship between object distance ($d_o$), image distance ($d_i$), and focal length ($f$), expressed as $\frac{1}{d_o} + \frac{1}{d_i} = \frac{1}{f}$.

Magnification ($m$)

The ratio of image height ($h_i$) to object height ($h_o$), given by $m = \frac{h_i}{h_o} = -\frac{d_i}{d_o}$.

Chromatic Aberration

An aberration where different wavelengths have different focal lengths because of light dispersion within the lens material.

Spherical Aberration

A defect in real lenses and mirrors where the curvature causes different rays to cross at different points rather than a single focal point.

Coma

An off-center image problem where rays do not converge correctly for angled views, often making an image look comet-like.

Concave Mirror

A converging mirror with a positive focal length ($f > 0$) where $f = \frac{R}{2}$; it can produce real or virtual images depending on the object distance.

Convex Mirror

A diverging mirror with a negative focal length ($f < 0$) that always produces a virtual, upright, and smaller image.

Huygens’s Principle

The principle stating that every point on a wavefront acts as a source of small wavelets that spread forward at the same speed as the original wave.

Diffraction

The property of waves where they bend or spread around edges or through openings.

Constructive Interference

Occurs when waves are in phase, such that their peaks add together to create a stronger wave.

Destructive Interference

Occurs when waves are out of phase, such that they cancel each other out.

Coherent Sources

Sources that produce light waves with a definite and constant phase relationship.

Diffraction Grating

A device with many slits that produces narrow, bright regions of constructive interference, often used in spectroscopy.

Rayleigh Criterion

The limit for resolving separate point sources, given for a circular aperture as $\theta \approx 1.22\frac{\lambda}{D}$.

Thin-Film Interference

The creation of bright colors in substances like soap bubbles or oil slicks due to interference between rays reflecting from the front and back surfaces of a film.

Reflection Phase Change

A $180^\circ$ phase change (equivalent to a $\frac{\lambda}{2}$ shift) that occurs when light reflects from a material with a higher index of refraction.