Physics: Waves, Sound, Light, and Optics

Comprehensive vocabulary flashcards reviewing wave classification, wave properties, sound phenomena, light reflection and refraction, total internal reflection, electromagnetic waves, and thin converging lenses.

Wave

The transfer of energy and information from one point to another without the transfer of particles.

Longitudinal Wave

A wave in which the particles of the medium vibrate parallel to the direction of wave propagation.

Transverse Wave

A wave in which the particles of the medium vibrate perpendicular to the direction of wave propagation.

Crest

The region of a transverse wave representing the maximum upward displacement of the particles of the medium.

Trough

The region of a transverse wave representing the maximum downward displacement of the particles of the medium.

Compression

A region in a longitudinal wave where the particles of the medium are closest together, corresponding to a high-pressure zone.

Rarefaction

A region in a longitudinal wave where the particles of the medium are spread farthest apart, corresponding to a low-pressure zone.

Amplitude

The maximum displacement of a vibrating particle from its undisturbed or original position.

Wavelength ($\lambda$)

The distance between two successive crests or troughs in a transverse wave, or between the centers of two successive compressions or rarefactions in a longitudinal wave.

Frequency ($f$)

The number of complete waves produced per second, measured in Hertz ($\text{Hz}$).

Periodic Time ($T$)

The time required to complete one full wave cycle, given by the relationship $T = \frac{1}{f}$.

Wave Speed ($v$)

The distance travelled by a wave in one second, calculated as the product of wavelength and frequency ($v = \lambda \times f$).

Wave Fronts

Equally spaced lines that are perpendicular to the direction of wave travel and represent adjacent crests, where the spacing between two successive lines equals the wavelength.

Law of Reflection

The rule stating that the angle of incidence equals the angle of reflection ($i = r$), with the incident ray, reflected ray, and normal all lying in the same plane.

Diffraction

The spreading out of waves as they pass through a narrow gap or around the edge of an obstacle, altering wave shape without affecting wavelength, wave speed, or frequency.

Mechanical Wave

A wave that requires a material medium to propagate and cannot travel through a vacuum (e.g., sound waves and water waves).

Audible Range

The range of sound frequencies detectable by the normal human ear, extending from $20\,\text{Hz}$ to $20{,}000\,\text{Hz}$.

Echo

A reflected sound heard distinctly after the original sound wave bounces off a hard, flat surface such as a wall or cliff.

Loudness

An auditory sensation governed by the amount of sound energy reaching the ear, directly determined by wave amplitude.

Pitch

The perceived sharpness or highness of a sound, determined directly by its frequency.

Sonar

A technique that uses transmitted pulses of ultrasound and their reflected echoes to determine water depth or detect underwater objects.

Ultrasound

Sound waves having frequencies higher than $20{,}000\,\text{Hz}$, which partially reflect at the boundary between different tissues or materials.

Luminous Source

An object that generates and radiates its own light, such as the Sun, lamps, or candles.

Non-Luminous Object

An object that cannot emit its own light and is visible only by reflecting light originating from a luminous source.

Normal

An imaginary construction line perpendicular to a surface at the point of incidence where a ray strikes it.

Real Image

An optical image formed by the actual intersection of light rays, which can be formed and projected onto a physical screen.

Virtual Image

An optical image formed where apparent ray extensions intersect, which cannot be captured or projected onto a screen.

Periscope

An optical device consisting of a tube containing two plane mirrors or prisms mounted parallel to each other at an angle of $45^\circ$, allowing an observer to view objects over barriers.

Refraction

The bending of a wave caused by a change in speed when it passes from one medium into another of different optical or physical density.

Refractive Index ($n$)

A dimensionless number quantifying how much light slows down and bends in a medium, defined mathematically as $n = \frac{\sin(i)}{\sin(r)}$.

Critical Angle ($c$)

The specific angle of incidence in an optically denser medium that produces an angle of refraction of $90^\circ$, causing light to graze the boundary surface.

Total Internal Reflection

The complete reflection of light back into a denser medium when the angle of incidence at the boundary with a rarer medium exceeds the critical angle ($i > c$).

Optical Fiber

A thin, flexible, transparent glass rod designed to carry light signals over long distances via repeated total internal reflections with minimal intensity loss.

Dispersion

The splitting of polychromatic white light into its constituent spectral colors when passing through a prism due to the differing refractive indices of each color.

Monochromatic Light

Light that consists of a single color, single wavelength, and specific frequency.

Electromagnetic Spectrum

The complete array of transverse waves made of combined oscillating electric and magnetic fields that travel at $3 \times 10^8\,\text{m/s}$ in a vacuum.

Geostationary Orbit

An orbit located approximately $35{,}000\,\text{km}$ above Earth's Equator where a satellite matches Earth's rotational rate, maintaining a constant position above one point.

Low Earth Orbit

A satellite orbit situated as low as $2{,}000\,\text{km}$ above Earth with periods as short as two hours, delivering low-latency communication over small areas.

Analogue Signal

An electric voltage signal that varies smoothly and continuously across a range of values over time.

Digital Signal

An electrical or optical signal that consists of discrete pulses representing distinct levels (typically High and Low).

Converging (Convex) Lens

A lens that refracts incident parallel light rays inward toward its central axis to meet at a single focal point.

Principal Focus ($F$)

The point on the principal axis of a converging lens where rays travelling parallel to the principal axis intersect after refraction.

Focal Length

The distance measured along the principal axis between the optical centre ($P$) of a lens and its principal focus ($F$).

Magnification

The ratio of the linear size or height of the image to the actual height of the object.

Short Sight (Myopia)

A vision defect where close objects are seen clearly while distant objects focus in front of the retina, corrected using a diverging lens.

Long Sight (Hyperopia)

A vision defect where distant objects are seen clearly while rays from close objects focus behind the retina, corrected using a converging lens.