Physics: Optics, Waves, Sound, and Electromagnetic Spectrum Flashcards

Vocabulary flashcards covering key definitions, laws, properties, and applications of Light, Reflection, Refraction, Lenses, Electromagnetic Spectrum, Sound Waves, and Wave Motion based on the lecture material.

Reflection of Light

The rebounding of light rays at a surface.

Normal (Optics)

An imaginary line perpendicular to the reflecting surface at the point of incidence.

Angle of Incidence ($i$)

The angle formed between the incident ray and the normal line at the point of incidence.

Angle of Reflection ($r$)

The angle formed between the reflected ray and the normal line at the point of incidence.

Law of Reflection

The physical law stating that the angle of incidence ($i$) is equal to the angle of reflection ($r$).

Refraction of Light

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

Snell's Law

The law stating that for two given media, the ratio of the sine of the angle of incidence ($i$) to the sine of the angle of refraction ($r$) is constant: $\frac{\sin(i)}{\sin(r)} = \text{constant}$.

Refractive Index ($n$)

The ratio of the speed of light in a vacuum to the speed of light in a medium ($n = \frac{\text{speed of light in vacuum}}{\text{speed of light in medium}}$), or $n = \frac{\sin(i)}{\sin(r)}$.

Critical Angle ($c$)

The angle of incidence in an optically denser medium for which the angle of refraction in the optically less dense medium is $90^\circ$, given by $\sin(c) = \frac{1}{n}$.

Total Internal Reflection

The complete reflection of a light ray inside an optically denser medium when the angle of incidence exceeds the critical angle ($i > c$).

Monochromatic Light

Light consisting of a single frequency or single wavelength.

Dispersion

The separation of white light into its component colors as a result of different wavelengths undergoing different degrees of refraction.

Convex Lens (Converging Lens)

A lens that is thicker in the center than at the edges, causing parallel light rays passing through it to converge at a focal point.

Concave Lens (Diverging Lens)

A lens that is thinner in the center than at the edges, causing parallel light rays passing through it to diverge.

Principal Focus ($F$)

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

Focal Length ($f$)

The distance between the optical center ($C$) of a lens and its principal focus ($F$).

Real Image

An image formed where light rays actually converge and intersect, which can be focused onto a screen.

Virtual Image

An image formed where light rays only appear to diverge from, which cannot be projected onto a screen.

Long-Sightedness (Hyperopia)

A vision defect where close objects focus behind the retina, which can be corrected using a converging (convex) lens.

Short-Sightedness (Myopia)

A vision defect where distant objects focus in front of the retina, which can be corrected using a diverging (concave) lens.

Electromagnetic Waves

Transverse waves formed by oscillating electric and magnetic fields that transfer energy at a speed of $3.0 \times 10^8\,\text{m/s}$ in a vacuum without requiring a medium.

Radio Waves

Electromagnetic waves with the longest wavelengths and lowest frequencies; used in TV, radio broadcasting, RFID, and astronomy.

Microwaves

Electromagnetic waves used in satellite communication, mobile phone networks, and cooking in microwave ovens.

Infrared Radiation

Electromagnetic radiation with wavelengths longer than visible red light; used in thermal imaging, remote controls, heating, and optical fibers.

Ultraviolet Radiation

Electromagnetic radiation with wavelengths shorter than visible violet light; used for sterilizing water, detecting fake banknotes, and sunbathing.

X-Rays

High-frequency electromagnetic waves capable of penetrating soft tissue but absorbed by dense materials like bones; used in medical scanning and airport security.

Gamma Rays

The highest-frequency electromagnetic radiation emitted by decaying radioactive nuclei; used to treat cancer and sterilize medical equipment.

Digital Signal

A signal that consists of discrete values representing high ('on' 1) and low ('off' 0), allowing noise to be filtered out and the original signal regenerated.

Analogue Signal

A signal that varies continuously over a smooth range of values.

Sound Wave

A longitudinal mechanical wave produced by a vibrating source that requires a material medium to propagate.

Compression (Sound)

A region in a longitudinal sound wave where medium particles are pressed close together and local pressure is higher than normal atmospheric pressure.

Rarefaction (Sound)

A region in a longitudinal sound wave where medium particles are spread further apart and local pressure is lower than normal atmospheric pressure.

Audible Range

The frequency band detectable by human ears, ranging from $20\,\text{Hz}$ to $20\,000\,\text{Hz}$.

Ultrasound

Sound waves with frequencies higher than $20\,000\,\text{Hz}$; used in non-destructive testing, medical scanning, and SONAR.

Infrasound

Sound waves with frequencies below $20\,\text{Hz}$.

Echo

A reflected sound wave heard after an interval due to bouncing off a hard, flat surface.

SONAR

Sound Navigation and Ranging; a technology using echo pulses of ultrasound to measure water depth or detect underwater objects.

Pitch

The perceived highness or lowness of a sound, directly determined by the frequency of the sound wave.

Loudness

The perceived volume of a sound, directly determined by the amplitude of the sound wave.

Transverse Wave

A wave in which particle vibration is perpendicular to the direction of wave propagation.

Longitudinal Wave

A wave in which particle vibration is parallel to the direction of wave propagation.

Crest

The highest point or maximum positive displacement on a transverse wave.

Trough

The lowest point or maximum negative displacement on a transverse wave.

Amplitude ($A$)

The maximum displacement of a wave particle from its undisturbed equilibrium position.

Wavelength ($\lambda$)

The distance between two consecutive points in phase on a wave, such as crest to crest or compression to compression.

Period ($T$)

The time required to complete one full wave cycle, measured in seconds ($\text{s}$).

Frequency ($f$)

The number of complete wave cycles generated per second, measured in Hertz ($\text{Hz}$), related to period by $f = \frac{1}{T}$.

Wavefront

An imaginary line connecting all adjacent points on a wave that are in phase with one another.

Diffraction

The spreading out of waves as they pass through a narrow gap or around the edge of an obstacle.