Nature and Properties of Light and Sound

A complete set of vocabulary flashcards covering key definitions, concepts, and quantitative details regarding light and sound waves from the lecture transcript.

Light Wave

A form of electromagnetic wave that travels very fast, does not need a medium, travels in straight lines, and can be reflected and refracted.

Speed of Light

The velocity of light in a vacuum, approximately $300,000\,\text{km/s}$ ($3 \times 10^8\,\text{m/s}$), which slows down in materials like glass or water.

Wavelength (\lambda)

The distance between two consecutive peaks or troughs of a wave, which determines the color of visible light.

Violet Light Wavelength

The visible wavelength spectrum range of $380-450\,\text{nm}$.

Blue Light Wavelength

The visible wavelength spectrum range of $450-495\,\text{nm}$.

Green Light Wavelength

The visible wavelength spectrum range of $495-570\,\text{nm}$.

Yellow Light Wavelength

The visible wavelength spectrum range of $570-590\,\text{nm}$.

Orange Light Wavelength

The visible wavelength spectrum range of $590-620\,\text{nm}$.

Red Light Wavelength

The visible wavelength spectrum range of $620-750\,\text{nm}$.

Frequency (f)

The number of wave cycles per second measured in Hertz ($\text{Hz}$), where higher frequency corresponds to more energy.

Speed of Light Formula

The equation relating speed, frequency, and wavelength: $c = f \times \lambda$.

Reflection

The process occurring when light bounces off a surface and returns to the original medium from which it originated without passing through.

Law of Reflection

The principle stating that the angle of incidence equals the angle of reflection ($\theta_i = \theta_r$), measured relative to the Normal line.

Normal Line

An imaginary line perpendicular to a reflective surface.

Specular Reflection

Reflection occurring on smooth, polished surfaces where light rays remain parallel, producing a clear, sharp image.

Diffuse Reflection

Reflection occurring on rough or irregular surfaces where light rays scatter in many directions, failing to produce a clear image.

Reflection in Plane Mirrors

Forms images that are virtual, upright, laterally inverted, the same size as the object, and located at an image distance equal to the object distance.

Concave Mirror

A mirror curved inward like a cave that can focus light to a Focal Point and produce real or virtual images depending on object position.

Real Image (Concave Mirror)

An image formed in front of a mirror when reflected rays actually meet (when the object is beyond the focus $F$); it is upside down and can be projected onto a screen.

Virtual Image (Concave Mirror)

An image formed behind a mirror when reflected rays appear to meet (when the object is between the focus $F$ and the mirror); it is upright, magnified, and cannot be projected onto a screen.

Convex Mirror

A mirror curved outward that spreads light rays apart, always producing virtual, upright, and diminished images while providing a wider field of view.

Refraction

The bending of light caused by a change in speed when light travels from one medium to another.

Index of Refraction (n)

The ratio of the speed of light in a vacuum to the speed of light in a medium ($n = \frac{c}{v}$).

Vacuum/Air Index of Refraction

An index of refraction value of $n \approx 1.00$.

Water Index of Refraction

An index of refraction value of $n \approx 1.33$.

Diamond Index of Refraction

An index of refraction value of $n \approx 2.42$.

Diffraction

The bending of waves around the edges of an obstacle or through a small opening.

Constructive Interference

Interference occurring when crest meets crest or trough meets trough, resulting in a stronger wave.

Destructive Interference

Interference occurring when crest meets trough, resulting in a weaker or canceled wave.

Polarization

A process using filters to allow light waves vibrating in only one direction to pass through.

Dispersion

The splitting of white light into its individual colors (e.g., in a prism) because different wavelengths travel at slightly different speeds and refract at different angles.

Sound Wave

A mechanical wave that requires a physical medium (air, water, or solids) to travel and cannot travel in outer space.

Human Hearing Range

The audible frequency range for humans, spanning from $20\,\text{Hz}$ to $20,000\,\text{Hz}$.

Wavelength of Sound

The distance between two successive compressions or rarefactions in a sound wave.

Amplitude (Sound)

The height of a sound wave that relates to its loudness, where greater amplitude yields louder sound.

Speed of Sound

The velocity of sound in a medium, measuring approximately $343\,\text{m/s}$ in air at $20^\circ\text{C}$ and $1500\,\text{m/s}$ in water.

Pitch

The perception of sound frequency indicating how high or low a sound sounds.

Loudness

The perception of wave amplitude, measured in decibels ($\text{dB}$).

Timbre (Quality)

The acoustic property that distinguishes different sources of sound from one another.

Echo

A phenomenon that occurs when sound waves reflect back after hitting a large surface and return after a short delay.