Optics, Waves, Electromagnetism, and Electricity Flashcards

Vocabulary flashcards covering key definitions in optics, wave mechanics, acoustics, electromagnetism, and current electricity from the provided lecture notes.

Luminous objects

Objects that produce light on their own, such as the sun, fire worms, or fireflies.

Non-luminous objects

Objects that do not produce light on their own but reflect light from luminous objects, such as the moon or stars.

Opaque objects

Objects that do not allow light to pass through them, such as wood, walls, or people.

Transparent objects

Objects that allow most light to pass through them, such as glass, clear water, or clear polythene.

Translucent objects

Objects that allow some light to pass through them, such as paper, bathroom glass, or tinted glass.

Ray

The direction of the path taken by light, indicated by a straight line with an arrow on it.

Beam

A collection of light rays or a stream of light energy.

Parallel beam

A light beam in which the constituent rays are parallel to each other, obtained from a distant light source or searchlights.

Convergent beam

A light beam in which rays from different directions meet at a common point, such as light passing through a convex lens.

Divergent beam

A light beam in which rays start from a common point and separate into different directions, such as light from a torch or car headlights.

Reflection

The bouncing of light as it strikes a reflecting surface.

Regular reflection

Reflection where an incident parallel beam is reflected as a parallel beam when light falls on a smooth surface like a plane mirror.

Irregular (diffuse) reflection

Reflection where an incident parallel beam is reflected in different directions when light falls on a rough surface.

Angle of incidence

The angle between the normal line and the incident ray.

Angle of reflection

The angle between the normal line and the reflected ray.

Sextant

An instrument used for measuring the angle of elevation of heavenly bodies such as the stars and the sun.

Real image

An image that can be formed on a screen and is formed by the actual intersection of light rays.

Virtual image

An image that cannot be formed on a screen and is formed by the apparent intersection of light rays.

Center of curvature

The center of the sphere of which a curved mirror or lens surface forms part.

Radius of curvature

The radius of the sphere of which a curved mirror or lens surface forms part.

Pole of the mirror

The mid-point (center) of a spherical mirror's surface.

Principal axis

The straight line passing through the center of curvature and the pole of a curved mirror (or joining the centers of curvature of a lens).

Paraxial rays

Rays of light close to the principal axis that make small angles with the mirror or lens axis.

Marginal rays

Rays of light furthest from the principal axis of a mirror or lens.

Linear magnification

The ratio of the image height to object height, or the ratio of image distance to object distance from the optical center or pole.

Caustic surface

A surface formed when reflected rays from a wide parallel beam incident on a concave mirror touch and form tangents, having an apex at the principal focus.

Refraction

The change of direction of light propagation as it travels from one medium to another due to a change in speed.

Refractive index

The ratio of the sine of the angle of incidence to the sine of the angle of refraction for light traveling from a vacuum into a medium, or the ratio of light speed in a vacuum to its speed in the medium.

Critical angle

The angle of incidence for which the angle of refraction is $90^\text{o}$ when light travels from a more optically dense medium to a less optically dense medium.

Total internal reflection

The reflection of light completely within an optically denser medium when the angle of incidence exceeds the critical angle.

Dispersion of white light

The separation of white light into its component colors by a transparent medium due to differences in speed of each color through the medium.

Visual angle

The angle subtended by an object or image at the eye.

Angular magnification

The ratio of the angle subtended by the final image at the eye when an instrument is used to the angle subtended by the object at the unaided eye.

Near point

The closest point at which the eye can focus clearly and view an object in greatest detail (least distance of distinct vision, $D = 25\,cm$).

Transverse waves

Waves in which the displacement of the particles in the medium is perpendicular to the direction of wave propagation.

Longitudinal waves

Waves in which the displacement of the particles in the medium is parallel to the direction of travel of the wave.

Amplitude

The maximum displacement of a medium particle from its equilibrium or rest position.

Wavelength

The distance between two successive particles in phase, such as two consecutive crests or troughs.

Frequency

The number of complete oscillations or cycles a wave particle makes in one second, measured in Hertz ($\text{Hz}$).

Progressive wave

A wave disturbance that travels from the source to surrounding regions, transferring energy along its path.

Stationary wave

A wave pattern formed by the superposition of two progressive waves of equal amplitude and frequency traveling at the same speed in opposite directions.

Pitch

The characteristic of sound by which the ear assigns a place on a musical scale, depending directly on frequency.

Reverberation

The prolonged sound heard when an echo follows the incident sound so closely that the listener cannot distinguish between the two.

Beats

A periodic rise and fall in the intensity of sound heard when two notes of nearly equal frequency but similar amplitude are sounded together.

Doppler Effect

The apparent change in frequency and wavelength of a wave when there is relative motion between the source of the waves and the observer.

Resonance

A condition obtained when a system is set to vibrate at its own natural frequency as a result of impulses received from another system vibrating at the same frequency.

Self-induction

The process of generating an induced e.m.f. in a coil due to a changing current in the same coil.

Mutual induction

The process of generating an e.m.f. in a secondary coil due to a changing current in a neighboring primary coil.

Magnetic flux density

The force acting on a $1\,m$ long conductor carrying a current of $1\,A$ perpendicular to a magnetic field, measured in Tesla ($\text{T}$).

Ohm's law

States that the current flowing through a conductor is directly proportional to the potential difference across its ends, provided temperature and other physical conditions remain constant.