Oscillations, Sound, and Light Practice Flashcards

Vocabulary-style flashcards based on lecture notes covering oscillations, sound interference, Doppler shift, standing waves, wave optics, diffraction, and ray optics including vision and lenses.

Constructive interference

Two or more waves that are in phase with one another at a specific location P, meaning they are at the exact same point in their cycle at every instant in time. This occurs when $\Delta(\text{cycles}) = m$ (where $m = 0, 1, 2, 3 \dots$).

Destructive interference

Two or more waves that are perfectly out-of-phase (half a cycle phase difference) with one another at a specific location P. This occurs when $\Delta(\text{cycles}) = \frac{1}{2}, \frac{3}{2}, \frac{5}{2} \dots$ and results in the waves cancelling each other out.

Beat frequency

The frequency ($f_b = |f_2 - f_1|$) at which an observer hears a sound alternate between loud and quiet due to the interference of two sound waves with similar but different frequencies.

Doppler shift

A change in observed frequency when either a source of sound or an observer moves in relation to each other, resulting in higher frequencies when moving toward one another and lower frequencies when moving away.

Standing wave

The sum of two traveling waves present in the same constrained medium at the same time, producing resonant frequencies where specific locations remain fixed (nodes) or reach maximum oscillation (antinodes).

Node

A location in a medium for a standing wave where the medium does not oscillate and remains at its equilibrium value for all time.

Antinode

A location in a medium for a standing wave in which the medium oscillates between its maximum and minimum values.

Electromagnetic (EM) wave

Coordinated electric and magnetic fields of oscillating strength that are perpendicular to one another and to the direction of wave travel (transverse waves).

Index of refraction (n)

A property of a material representing the factor by which an EM wave slows down in that material compared to its speed in vacuum, calculated as $v = \frac{c}{n}$.

Diffraction

The spreading out of a wave after it passes through a slit or moves around a barrier when the width is on the order of the wavelength.

Double-slit interference setup

The process where a single plane wave passes through two narrow slits to create a pattern of bright and dark spots (maxima and minima) based on the path difference $|\Delta r| = d \sin(\theta)$.

Surface normal

A line drawn perpendicular to an interface or boundary between two materials at the location where an incoming light ray intersects the interface.

X-ray diffraction

The use of x-rays on a solid to determine the positions of atoms or molecules, characterized by the interference condition $2d \sin(\theta) = |\Delta r| = m\lambda$.

Snell's Law

The principle that relates the indices of refraction of two media and the angles of incidence and transmission ($n_i \sin(\theta_i) = n_t \sin(\theta_t)$) when light crosses an interface.

Real object

An object from which light rays physically diverge as they move away, such as a light bulb, or objects that reflect light similarly like a pencil.

Real image

An image formed at the location where at least two rays of light originating from a single point on the object physically intersect.

Virtual image

An image formed where light rays appearing to originate from the object do not physically intersect at the image location, but appear to do so to an observer.

Focal point (f)

The point where light rays approaching parallel to the axis of a lens or mirror intersect (real) or appear to intersect (virtual).

Converging lens

A lens thicker in the center than at the edges that focuses incoming light rays toward a real focal point on the opposite side.

Diverging lens

A lens thinner in the center than at the edges that spreads incoming light rays farther apart, so they appear to intersect at a virtual focal point on the same side.

Diopter (D)

A unit of measure for the power of a lens calculated as the inverse of the focal length in meters ($D = \frac{1}{f}$).

Near point (N)

The closest distance to the eye where an object can be placed and still form a clear image on the retina; for a normal eye, this is $25\,cm$.

Far point (F)

The farthest distance from the eye where an object can be placed and still form a clear image on the retina; for a normal eye, this is infinitely far away.

Nearsightedness (Myopia)

A condition where the eye's far point is closer than infinity ($F_{ns} < F_{\text{normal}}$), often because the eye lens is too strong or the eye is too long.

Farsightedness (Hyperopia)

A condition where the eye's near point is farther than normal ($N_{fs} > N_{\text{normal}}$), often because the eye lens is too weak or the eye is too short.

Simple magnifier

A converging lens used to create an enlarged virtual image of an object placed at or inside the focal point ($M = \frac{N}{f}$).

Microscope

An optical instrument using an objective lens and an eyepiece to create highly enlarged images, with total magnification $M = - \frac{N \ell}{f_o f_e}$.