DEFINITIONS : PHYSICS

• Reflection(of light): The bouncing back of a ray of light after striking the surface of an object is called reflection of light.


• Concave Mirror: A spherical mirror, whose reflecting surface is curved inwards, i.e., it faces towards the centre of the sphere, is called a concave mirror.


• Convex Mirror: A spherical mirror, whose reflecting surface is curved outwards, i.e., the centre of the sphere is behind the reflecting surface, is called a convex mirror.


• Pole(of a mirror): The centre of the reflecting surface of a spherical mirror is called the pole of the mirror.


• Centre of Curvature: The centre of the sphere of which the mirror(or lens) is a part, is called the centre of curvature of that mirror(or lens).


• Radius of Curvature: The radius of the sphere of which the mirror(or lens) is a part, is called the radius of curvature of that mirror(or lens).


• Principal Axis of a Mirror: An imaginary straight line passing through the pole and the centre of curvature of a spherical mirror is called the principal axis of that mirror.


• Principal Focus of a Mirror: The point, on the principal axis of a spherical mirror, at which the rays parallel to the principal axis meet or appear to meet after reflection is called the principal focus of that mirror.


• Focal Length of a Mirror: The distance between the pole and the principal focus of a spherical mirror is called focal length of that mirror.


• Aperture of a Mirror: The diameter of the reflecting surface of a spherical mirror is called the aperture of the mirror.


• Magnification: The ratio of the height of the image to the height of the object is called magnification.


• Refraction: The phenomenon in which the direction of a light ray changes when it enters from one medium to another medium, is called refraction.


• Absolute Refractive Index: The ratio of the speed of light in vacuum to that in a medium is called the absolute refractive index of that medium.[Generally absolute refractive index is referred to as Refractive index].


• Relative Refractive Index: The ratio of the speed of light in one medium to that in another medium is called (Relative) refractive index of second medium with respect to the first medium.


• Convex Lens: A lens having two spherical surfaces bulging outwards is called a convex lens.[we use convex in place of biconvex for the sake of convenience].


• Concave Lens: A lens having two spherical surfaces curved inwards is called a concave lens.[we use concave in place of biconcave for the sake of convenience].


• Optical Centre: The central point of a lens is called optical centre of the lens.


• Principal Axis of a Lens: An imaginary straight line passing through the two centres of curvature of a lens is called the principalaxis of the lens.


• Aperture of a Lens: The effective diameter of the circular outline of a spherical lens is called the aperture of the lens.


• Principal Focus of a Lens: The point on the principal axis of a lens at which the rays parallel to the principal axis meet or appear to meet after refraction, is called the principal focus of the lens.


• Focal Length of a Lens: The distance between optical centre and the principal focus of a lens is called the focal length of the lens.


• Power of a Lens: The reciprocal of the focal length of a lens is called power of the lens.


• Power of Accommodation: The ability of the eye lens to adjust its focal length in such a way that the image of the object is formed exactly on retina, is called the power of accommodation (of eyes).


• Least Distance of Distinct vision(Near Point of the Eye): The minimum distance, at which objects can be seen most distinctly without strain, is called least distance of distinct vision.


• Far Point of the Eye: The farthest point up to which the eye can see objects clearly, is called Far point of the eye.


• Angle of Prism: The angle between two lateral faces of a prism is called the prism angle.


• Angle of Deviation: The angle between the incident ray and the emergent ray is called the angle of deviation.


• Dispersion of Light: The splitting of light into its constituent colours is called dispersion of light.


• Spectrum: The group of bands of different component colours of a light beam is called a spectrum.


• Electric Current: The continuous flow of electric charge(electrons) through a conductor(wire) is called electric current.


• Electric Circuit: A continuous and closed path through which electric current can pass is called electric circuit.


• 1-Ampere Current: When one coulomb of charge passes through a point of a conductor per second, the current is said to be 1-ampere current.


• Electric Potential difference: The work done to move a unit charge from one point to the other in an electric field is called the electric potential difference between those two points.


• 1-Volt Potential Difference: When one joule of work is done to move a charge of 1 coulomb from one point to the other in an electric field, the potential difference between those two points is called 1 volt.


• Resistance: It is the property of a conductor by which it(the conductor) opposes the movement of electric charge through it.


• 1-Ohm Resistance: When the potential difference between the terminals of a conductor carrying one ampere current is one volt, its resistance is 1 ohm.


• Resistor: A conductor having some appreciable resistance is called resistor.


• Insulator: A component which offers very high resistance so that practically no current can pass through it is called insulator.


• Resistivity: It is a characteristic property of the material of a conductor on which the resistance offered by the conductor depends.


• Electric power: The rate at which electric energy is dissipated or consumed by an equipment is called its power.


• Direct Current: The current which flows in only one direction and does not change its direction with time is called direct current.


• Alternating Current: The current which changes its direction between two terminals periodically is called alternating current.


• Overloading: A situation in which the current flowing in a circuit increases beyond the current it can hold is called overloading.


• Short-Circuiting A situation created due to the direct contact of the live wire and the neutral wire in which the current increases abruptly resulting in overloading is called short-circuiting.