Science Light – Reflection and Refraction Flashcards

Comprehensive vocabulary flashcards covering the concepts, laws, and formulas of reflection and refraction of light from Chapter 9.

Ray of light

The straight-line path of light indicated when a small source of light casts a sharp shadow of an opaque object.

Diffraction of light

The effect known to occur when an opaque object on the path of light becomes very small, causing light to bend around it instead of walking in a straight line.

Quantum theory of light

A modern theory in which light is neither a ‘wave’ nor a ‘particle’, reconciling particle properties with the wave nature.

Laws of Reflection (i)

The law stating that the angle of incidence is equal to the angle of reflection.

Laws of Reflection (ii)

The law stating that the incident ray, the normal to the mirror at the point of incidence and the reflected ray, all lie in the same plane.

Spherical mirrors

Mirrors whose reflecting surfaces are spherical, considered to form a part of the surface of a sphere.

Concave mirror

A spherical mirror whose reflecting surface is curved inwards, meaning it faces towards the centre of the sphere.

Convex mirror

A spherical mirror whose reflecting surface is curved outwards.

Pole ($P$)

The point representing the centre of the reflecting surface of a spherical mirror, lying on the surface of the mirror.

Centre of curvature ($C$)

The centre of the sphere of which the reflecting surface of a spherical mirror forms a part; it lies outside the reflecting surface.

Radius of curvature ($R$)

The radius of the sphere of which the reflecting surface of a spherical mirror forms a part; the distance $PC$ is equal to this value.

Principal axis

An imaginary straight line passing through the pole and the centre of curvature of a spherical mirror, which is normal to the mirror at its pole.

Principal focus ($F$) of a concave mirror

The point on the principal axis where rays parallel to the principal axis meet or intersect after reflection.

Principal focus ($F$) of a convex mirror

The point on the principal axis from which reflected rays, originally parallel to the principal axis, appear to come.

Focal length ($f$)

The distance between the pole and the principal focus of a spherical mirror.

Aperture

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

Relationship between Radius and Focal Length

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

Object distance ($u$)

The distance of the object from the pole of a spherical mirror or the optical centre of a lens.

Image distance ($v$)

The distance of the image from the pole of a spherical mirror or the optical centre of a lens.

Mirror formula

The relationship between object distance ($u$), image distance ($v$), and focal length ($f$) expressed as $\frac{1}{v} + \frac{1}{u} = \frac{1}{f}$.

Magnification ($m$)

The relative extent to which the image of an object is magnified with respect to the object size, given by the ratio of the height of the image ($h'$) to the height of the object ($h$).

Refraction of light

The phenomenon in which the direction of propagation of light changes when travelling obliquely from one transparent medium to another.

Snell’s law of refraction

The law stating that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, expressed as $\frac{\text{sin}(i)}{\text{sin}(r)} = \text{constant}$.

Speed of light in vacuum

The highest speed at which light travels, which is $3 \times 10^8\text{ m s}^{-1}$.

Refractive index ($n_{21}$)

The ratio of the speed of light in medium 1 ($v_1$) to the speed of light in medium 2 ($v_2$), expressed as $n_{21} = \frac{v_1}{v_2}$.

Absolute refractive index ($n_m$)

The refractive index of a medium with respect to vacuum or air, calculated as $n_m = \frac{c}{v}$ where $c$ is the speed of light in air and $v$ is the speed of light in the medium.

Optical density

The ability of a medium to refract light; it is not the same as mass density.

Convex lens

A double convex lens that is thicker at the middle than at the edges and converges light rays; also called a converging lens.

Concave lens

A double concave lens that is thicker at the edges than at the middle and diverges light rays; also called a diverging lens.

Optical centre ($O$)

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

Lens formula

The mathematical relationship between object distance ($u$), image distance ($v$), and focal length ($f$) for a lens, expressed as $\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$.

Power of a lens ($P$)

The degree of convergence or divergence of light rays achieved by a lens, defined as the reciprocal of its focal length ($f$), given by $P = \frac{1}{f}$.

Dioptre ($D$)

The SI unit of power of a lens; $1\text{ dioptre}$ is the power of a lens whose focal length is $1\text{ metre}$ ($1D = 1\text{ m}^{-1}$).