Physics Lecture: Waves, Electricity, and Optics

This set of vocabulary flashcards covers essential definitions regarding waves, electricity, magnetism, and geometric optics based on the student's lecture notes.

Wave

A distortion in a material or medium where individual parts show periodic motion, but the waveform itself moves through the material.

Transverse wave

A wave where the direction of oscillation of a particle is perpendicular to the direction of propagation of the wave.

Longitudinal wave

A wave where the direction of oscillation of a particle is the same as the direction of propagation of the wave.

Constructive interference

Occurs when two identical wavefronts travel toward each other so maximum amplitudes coincide, resulting in a new wavefront with the same frequency but twice the amplitude ($\text{addition of positive amplitudes}$).

Destructive interference

Occurs when two identical wavefronts travel toward each other, but the maximum positive amplitude of wave 1 coincides with the maximum negative amplitude of wave 2 ($\text{cancelling out of positive and negative amplitude}$).

Beats

A phenomenon that occurs when two waves are present and there is a small difference in frequency between them.

Beat frequency

The absolute value of the difference in frequency of the two waves.

Principle of Linear Superposition

When two or more waves are present simultaneously at the same place, the resultant disturbance is the sum of the disturbances from the individual waves.

Good conductors

Materials that conduct heat and electricity well.

Good insulators

Materials that conduct heat and electricity very poorly.

Voltage (in a electric circuit)

The work done or energy transferred per unit charge between two points in an electrical circuit, defined by $V = \frac{W}{Q}$ or $V = \frac{\Delta E}{Q}$.

Electric potential at a point

The electric potential $V$ at a given point is the electric potential energy $EPE$ of a small test charge $q_0$ situated at that point, divided by the charge itself ($V = \frac{EPE}{q_0}$).

Current

The rate of flow of charge, defined as $I = \frac{\Delta q}{\Delta t}$, where $1\,\text{Coulomb} \cdot \text{s}^{-1} = 1\,\text{Amp (A)}$.

Law of Conservation of Charge

During any process, the net electric charge of an isolated system remains constant.

Direct Current

Current that always flows in the same direction (e.g., a battery).

Alternating Current

Current that constantly changes direction (e.g., a plug).

Conventional Current

The flow of positive charge from the positive terminal to the negative terminal, though in reality electrons move from the negative terminal to the positive terminal.

Resistance

A property of a metal wire that depends on the wire's length $L$ and cross-sectional area $A$.

Resistivity

An intrinsic property of a material defined as the resistance of a piece of that material that is $1\,\text{m}$ long and has a cross sectional area of $1\,\text{m}^2$.

Magnetism

A natural force produced by moving electric charges that is fundamentally linked to electricity.

Magnetic field

A vector field surrounding a magnet or moving charge that exerts force on other moving charges, denoted by the symbol $B$ and measured in Tesla $(T)$.

Electromagnetism

The physical interaction between electric fields and magnetic fields produced by charged particles, which can interact to form electromagnetic waves.

Geometric optics

The study of the behavior of light by treating it as rays that travel in straight lines.

Light Rays

Straight-line paths used to show the direction of propagation of light.

Wavefront

A surface perpendicular to light rays connecting all points of a wave that have the same phase.

Law of reflection

The incident ray, reflected ray, and the normal lie in the same plane, and the angle of incidence equals the angle of reflection.

Concave mirror

A mirror with a surface that reflects parallel rays toward a focal point and can form real or virtual images.

Convex mirror

A mirror that reflects rays outward and always forms virtual images.

Specular reflection

Reflection from smooth surfaces where parallel incoming rays remain parallel after reflection, producing clear images.

Diffuse reflection

Reflection from rough surfaces where parallel incoming rays are reflected in many directions, resulting in no clear image.

Focal point

The point where parallel rays converge after reflection in a concave mirror.

Radius of Curvature (R)

The distance between the mirror surface and the center of curvature.

Centre of Curvature (C)

The point that is the center of the sphere from which the mirror surface is derived.

Principal Axis

A straight line passing through the center of curvature and the mirror pole (center of the mirror).

Virtual image

An image formed at a point from which light rays appear to diverge but do not actually pass; it is upright and not projectable onto a screen.

Real image

An image formed at a point where light rays actually converge and pass through; it is inverted and projectable onto a screen.

Refraction

The bending of light when it passes from one medium to another due to a change in speed.

Total internal reflection (TRI)

Occurs when light traveling in a higher refractive index medium strikes a boundary with a lower refractive index medium at an angle exceeding the critical angle, causing the light to be completely reflected.

Critical angle

The smallest angle of incidence that produces total internal reflection.