Light: Reflection and Refraction - Chapter 9 Flashcards

This flashcard set covers the vocabulary and essential formulas defined in the lecture notes on Light - Reflection and Refraction, including mirror and lens properties, laws of optics, and sign conventions.

Diffraction of light

An effect where light has a tendency to bend around a very small opaque object on its path and not walk in a straight line.

Mirror

A highly polished surface that reflects most of the light falling on it.

Laws of reflection

(i) The angle of incidence is equal to the angle of reflection, and (ii) 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, facing towards 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, usually represented by the letter $P$.

Centre of curvature

The centre of the sphere of which the reflecting surface of a spherical mirror forms a part, represented by the letter $C$.

Radius of curvature

The radius of the sphere of which the reflecting surface of a spherical mirror forms a part, represented by the letter $R$.

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 of a concave mirror

The point on the principal axis where rays parallel to the principal axis meeting or intersect after reflecting from the mirror.

Focal length

The distance between the pole and the principal focus of a spherical mirror, represented by the letter $f$.

Aperture

The diameter of the reflecting surface of a spherical mirror.

Relationship between radius of curvature ($R$) and focal length ($f$)

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

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

Refraction of light

The phenomenon of the change in direction of propagation of light when it travels obliquely from one transparent medium to another.

Snell’s law of refraction

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

Refractive index ($n_{21}$)

The ratio of the speed of light in medium 1 ($v_1$) to the speed of light in medium 2 ($v_2$).

Absolute refractive index ($n_m$)

The refractive index of a medium with respect to vacuum or air, given by $n_m = \frac{c}{v}$, where $c$ is the speed of light in air ($3 \times 10^8\,m\,s^{-1}$).

Optical density

The ability of a medium to refract light; an optically denser medium has a larger refractive index and a lower speed of light than an optically rarer medium.

Convex lens

A lens bound by two spherical surfaces bulging outwards, which is thicker at the middle than at the edges; also known as a converging lens.

Concave lens

A lens bounded by two spherical surfaces curved inwards, which is thicker at the edges than at the middle; also known as a diverging lens.

Optical centre

The central point of a lens, represented by the letter $O$, through which a ray of light passes without suffering any deviation.

Lens formula

The 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 reciprocal of the focal length ($f$) of a lens, expressed as $P = \frac{1}{f}$.

Dioptre ($D$)

The SI unit of power of a lens, where $1\,D = 1\,m^{-1}$.