Light - Reflection and Refraction

Vocabulary practice flashcards covering key definitions, principles, and formulas from the Chapter on Light - Reflection and Refraction.

Diffraction of light

The phenomenon where light bends around a very small opaque object placed in its path instead of propagating in a straight line.

Quantum theory of light

A modern physical theory in which light is regarded as neither purely a 'wave' nor a 'particle', reconciling its particle properties with its wave nature.

Laws of reflection

The principles stating that (i) the angle of incidence is equal to the angle of reflection, and (ii) the incident ray, the normal at the point of incidence, and the reflected ray all lie in the same plane.

Spherical mirror

A mirror whose reflecting surface is curved and forms part of a spherical surface.

Concave mirror

A spherical mirror whose reflecting surface is curved inwards, facing toward the centre of the sphere.

Convex mirror

A spherical mirror whose reflecting surface is curved outwards.

Pole

The centre of the reflecting surface of a spherical mirror, situated on the mirror surface and represented by the letter $P$.

Centre of curvature

The point $C$ that forms the centre of the sphere of which the reflecting surface of a spherical mirror is a part.

Radius of curvature

The radius $R$ of the sphere of which the reflecting surface of a spherical mirror forms a part, corresponding to distance $PC$.

Principal axis

A straight line passing through the pole $P$ and centre of curvature $C$ of a spherical mirror, acting normal to the mirror at its pole.

Principal focus of a concave mirror

The point $F$ on the principal axis where rays parallel to the principal axis intersect after reflecting off a concave mirror.

Principal focus of a convex mirror

The point $F$ on the principal axis from which rays parallel to the principal axis appear to diverge after reflecting off a convex mirror.

Focal length

The distance $f$ between the pole (or optical centre) and the principal focus of a spherical mirror or lens.

Aperture

The diameter of the reflecting surface of a spherical mirror or the effective diameter of the circular outline of a spherical lens.

Relationship between radius of curvature and focal length

For spherical mirrors of small apertures, the radius of curvature is equal to twice the focal length, represented as $R = 2f$.

Mirror formula

The formula relating object distance ($u$), image distance ($v$), and focal length ($f$) for a spherical mirror, expressed as $\frac{1}{v} + \frac{1}{u} = \frac{1}{f}$.

Magnification (spherical mirror)

The ratio of the image height ($h'$) to the object height ($h$), which can also be expressed as $m = -\frac{v}{u}$.

Refraction of light

The phenomenon where light changes its direction of propagation when travelling obliquely from one transparent medium to another due to a change in light speed.

Snell’s law of refraction

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

Absolute refractive index

The ratio of the speed of light in vacuum or air ($c$) to the speed of light in a given medium ($v$), represented as $n_m = \frac{c}{v}$.

Optically denser medium

A transparent medium with a higher refractive index relative to another medium, causing light to travel slower and bend toward the normal.

Optically rarer medium

A transparent medium with a lower refractive index relative to another medium, causing light to travel faster and bend away from the normal.

Convex lens

A double convex lens bound by two spherical surfaces bulging outwards, thicker in the middle than at the edges, which converges light rays.

Concave lens

A double concave lens bound by two spherical surfaces curved inwards, thicker at the edges than in the middle, which diverges light rays.

Optical centre

The central point $O$ of a lens through which a ray of light passes without suffering any deviation.

Lens formula

The relation connecting object distance ($u$), image distance ($v$), and focal length ($f$) for a spherical lens, given as $\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$.

Power of a lens

A measure of the degree of convergence or divergence of light rays achieved by a lens, defined as the reciprocal of its focal length in metres: $P = \frac{1}{f}$.

Dioptre

The SI unit of power of a lens, denoted as $\text{D}$, defined as the power of a lens whose focal length is $1\,\text{m}$ ($1\,\text{D} = 1\,\text{m}^{-1}$).