 Light is a form of energy which produces the sensation of sight.  Speed of light in vacuum / air = 3 × 108 ms–1  Ray of light : A line drawn in the direction of propagation of light is called ray of light.  Beam of light : A group of parallel rays light emitted by a source of light is called beam of light.  Reflection of light : The phenomenon of returning of light in the same medium after striking a surface is called reflection of light.  Laws of reflection : The reflection of light from a surface obeys certain laws called laws of reflection. (i) incident angle is equal to reflected angle i.e. i = r. (ii) Incident ray, reflected ray and normal to the reflecting surface at the point on incident lie in the same plane.  Concave mirror : concave mirror is a part of a hollow sphere whose outer part is silvered and the inner part is reflecting surface.  Convex mirror : convex mirror is a part of a hollow sphere whose outer part is reflecting surface and inner part is silvered.  Centre of curvature : The centre of a hollow sphere of which the spherical mirror forms a part is called centre of curvature. It is denoted by C  Radius of curvature : The radius of a hollow sphere of which the spherical mirror forms a part is called radius of curvature. It is denoted by R  Pole : The mid point of a spherical mirror is called its pole. It is denoted by P  Aperture: The part of spherical mirror exposed to the incident light is called the aperture of the mirror.  Principal Axis: A line joining the centre of curvature (C) and pole (P) of a spherical mirror and extend on either side is called principal axis of the spherical mirror.  Principal Focus : A point on the principal axis of a spherical mirror where the rays of light parallel to the principal axis meet or appears to meet after reflection from the spherical mirror is called principal focus. It is denoted by F.  Focal Plane : A plane normal or perpendicular to the principal axis and passing through the principal focus (F) of the spherical mirror is called focal plane of the spherical mirror.  Focal length (f): The distance between the pole (P) and the principal focus (F) of a spherical mirror is called the focal length of the spherical mirror.  f = , Where R is the radius of the curvature of the mirror.  Focal length and radius of curvature of a concave mirror are negative.  Focal length and radius of curvature of a convex mirror are positive.  Sign Conventions for reflection by spherical mirrors (1) All distance are measured from the pole of a spherical mirror. (2) Distance measured in the direction of incident light are taken as positive. Distance measured in the direction opposite to that of the incident light are taken negative. (3) The upward distance perpendicular to the principal axis are taken as positive, while the downward distance perpendicular to the principal axis are taken as negative.  Radius of curvature plane mirror =  ( infinite)  Focal length of a plane mirror =   Mirror Formula : The relation between u, v, and focal length (f) of a spherical mirror is known as mirror formula. That is  Linear magnification : Linear magnification produced by a mirror is defined as the ratio of the size ( or height) of the image to the size of the object . It is denoted by m. That is  Power of mirror (P) = =  Linear magnification produced by a plane mirror = + 1.  Refraction of light: The bending of light rays when they pass obsessively from one medium to the other medium is called refraction of light .  A transparent medium through which light travels fast is known as optically rarer medium.  A transparent medium through which light travels slow is known as optically denser medium.  Laws of refraction (i) The incident ray, the refracted ray and the normal to the surface separating two media all lie in the same plane. (ii) The ratio of the sine of the incident angle (i) to the sine of the refracted angle (r) is constant i.e. sin i/ sin r = constant This constant is known as the refractive index of second medium w.r.t the first medium.  Absolute refractive index of a medium is defined as the ratio of the speed of light in vacuum (c) to the speed of light in the medium (v) i.e. n = c / v  Relative refractive index of medium. 2 w.r.t. the medium 1 is defined as the ratio of the speed of light in medium 1 (v1) to the speed of light in medium 2 (v2). i.e. n21= v2 / v1

 Light is a form of energy which produces the sensation of sight.  Speed of light in vacuum / air = 3 × 108 ms–1  Ray of light : A line drawn in the direction of propagation of light is called ray of light.  Beam of light : A group of parallel rays light emitted by a source of light is called beam of light.  Reflection of light : The phenomenon of returning of light in the same medium after striking a surface is called reflection of light.  Laws of reflection : The reflection of light from a surface obeys certain laws called laws of reflection. (i) incident angle is equal to reflected angle i.e. i = r. (ii) Incident ray, reflected ray and normal to the reflecting surface at the point on incident lie in the same plane.  Concave mirror : concave mirror is a part of a hollow sphere whose outer part is silvered and the inner part is reflecting surface.  Convex mirror : convex mirror is a part of a hollow sphere whose outer part is reflecting surface and inner part is silvered.  Centre of curvature : The centre of a hollow sphere of which the spherical mirror forms a part is called centre of curvature. It is denoted by C  Radius of curvature : The radius of a hollow sphere of which the spherical mirror forms a part is called radius of curvature. It is denoted by R  Pole : The mid point of a spherical mirror is called its pole. It is denoted by P  Aperture: The part of spherical mirror exposed to the incident light is called the aperture of the mirror.  Principal Axis: A line joining the centre of curvature (C) and pole (P) of a spherical mirror and extend on either side is called principal axis of the spherical mirror.  Principal Focus : A point on the principal axis of a spherical mirror where the rays of light parallel to the principal axis meet or appears to meet after reflection from the spherical mirror is called principal focus. It is denoted by F.  Focal Plane : A plane normal or perpendicular to the principal axis and passing through the principal focus (F) of the spherical mirror is called focal plane of the spherical mirror.  Focal length (f): The distance between the pole (P) and the principal focus (F) of a spherical mirror is called the focal length of the spherical mirror.  f = , Where R is the radius of the curvature of the mirror.  Focal length and radius of curvature of a concave mirror are negative.  Focal length and radius of curvature of a convex mirror are positive.  Sign Conventions for reflection by spherical mirrors (1) All distance are measured from the pole of a spherical mirror. (2) Distance measured in the direction of incident light are taken as positive. Distance measured in the direction opposite to that of the incident light are taken negative. (3) The upward distance perpendicular to the principal axis are taken as positive, while the downward distance perpendicular to the principal axis are taken as negative.  Radius of curvature plane mirror =  ( infinite)  Focal length of a plane mirror =   Mirror Formula : The relation between u, v, and focal length (f) of a spherical mirror is known as mirror formula. That is  Linear magnification : Linear magnification produced by a mirror is defined as the ratio of the size ( or height) of the image to the size of the object . It is denoted by m. That is  Power of mirror (P) = =  Linear magnification produced by a plane mirror = + 1.  Refraction of light: The bending of light rays when they pass obsessively from one medium to the other medium is called refraction of light .  A transparent medium through which light travels fast is known as optically rarer medium.  A transparent medium through which light travels slow is known as optically denser medium.  Laws of refraction (i) The incident ray, the refracted ray and the normal to the surface separating two media all lie in the same plane. (ii) The ratio of the sine of the incident angle (i) to the sine of the refracted angle (r) is constant i.e. sin i/ sin r = constant This constant is known as the refractive index of second medium w.r.t the first medium.  Absolute refractive index of a medium is defined as the ratio of the speed of light in vacuum (c) to the speed of light in the medium (v) i.e. n = c / v  Relative refractive index of medium. 2 w.r.t. the medium 1 is defined as the ratio of the speed of light in medium 1 (v1) to the speed of light in medium 2 (v2). i.e. n21= v2 / v1

 Light is a form of energy which produces the sensation of sight.  Speed of light in vacuum / air = 3 × 108 ms–1  Ray of light : A line drawn in the direction of propagation of light is called ray of light.  Beam of light : A group of parallel rays light emitted by a source of light is called beam of light.  Reflection of light : The phenomenon of returning of light in the same medium after striking a surface is called reflection of light.  Laws of reflection : The reflection of light from a surface obeys certain laws called laws of reflection. (i) incident angle is equal to reflected angle i.e. i = r. (ii) Incident ray, reflected ray and normal to the reflecting surface at the point on incident lie in the same plane.  Concave mirror : concave mirror is a part of a hollow sphere whose outer part is silvered and the inner part is reflecting surface.  Convex mirror : convex mirror is a part of a hollow sphere whose outer part is reflecting surface and inner part is silvered.  Centre of curvature : The centre of a hollow sphere of which the spherical mirror forms a part is called centre of curvature. It is denoted by C  Radius of curvature : The radius of a hollow sphere of which the spherical mirror forms a part is called radius of curvature. It is denoted by R  Pole : The mid point of a spherical mirror is called its pole. It is denoted by P  Aperture: The part of spherical mirror exposed to the incident light is called the aperture of the mirror.  Principal Axis: A line joining the centre of curvature (C) and pole (P) of a spherical mirror and extend on either side is called principal axis of the spherical mirror.  Principal Focus : A point on the principal axis of a spherical mirror where the rays of light parallel to the principal axis meet or appears to meet after reflection from the spherical mirror is called principal focus. It is denoted by F.  Focal Plane : A plane normal or perpendicular to the principal axis and passing through the principal focus (F) of the spherical mirror is called focal plane of the spherical mirror.  Focal length (f): The distance between the pole (P) and the principal focus (F) of a spherical mirror is called the focal length of the spherical mirror.  f = , Where R is the radius of the curvature of the mirror.  Focal length and radius of curvature of a concave mirror are negative.  Focal length and radius of curvature of a convex mirror are positive.  Sign Conventions for reflection by spherical mirrors (1) All distance are measured from the pole of a spherical mirror. (2) Distance measured in the direction of incident light are taken as positive. Distance measured in the direction opposite to that of the incident light are taken negative. (3) The upward distance perpendicular to the principal axis are taken as positive, while the downward distance perpendicular to the principal axis are taken as negative.  Radius of curvature plane mirror =  ( infinite)  Focal length of a plane mirror =   Mirror Formula : The relation between u, v, and focal length (f) of a spherical mirror is known as mirror formula. That is  Linear magnification : Linear magnification produced by a mirror is defined as the ratio of the size ( or height) of the image to the size of the object . It is denoted by m. That is  Power of mirror (P) = =  Linear magnification produced by a plane mirror = + 1.  Refraction of light: The bending of light rays when they pass obsessively from one medium to the other medium is called refraction of light .  A transparent medium through which light travels fast is known as optically rarer medium.  A transparent medium through which light travels slow is known as optically denser medium.  Laws of refraction (i) The incident ray, the refracted ray and the normal to the surface separating two media all lie in the same plane. (ii) The ratio of the sine of the incident angle (i) to the sine of the refracted angle (r) is constant i.e. sin i/ sin r = constant This constant is known as the refractive index of second medium w.r.t the first medium.  Absolute refractive index of a medium is defined as the ratio of the speed of light in vacuum (c) to the speed of light in the medium (v) i.e. n = c / v  Relative refractive index of medium. 2 w.r.t. the medium 1 is defined as the ratio of the speed of light in medium 1 (v1) to the speed of light in medium 2 (v2). i.e. n21= v2 / v1

 Energy is the essential requirement for each and every activity in our life.  The various sources of energy are the sun, the wind, water, fossil fuels etc.  The sun is the ultimate source of all forms of energy.  A good source of energy is one which supplies large amount of useful energy, easily available, economical and cause minimum environmental pollution. .  Thermal power plant generates electricity by burning fossil fuel like coal and oil.  LPG is a petroleum gas liquefied under pressure. Its full form is liquefied Petroleum Gas.  CNG is compressed Natural Gas.  Main constituents of CNG is methane.  Electricity produced by flowing water is known as hydro - electric power.  A plant used to produce hydro -electric power is known as hydro -electric power plant.  Potential energy of water stored in a dam is converted into kinetic energy of the falling water. This kinetic energy of falling water is converted into the kinetic energy of the armature of the generator which in turn is converted into electric energy.  Biomass is material which contains carbon and other combustible material.  Plants, wood animals and plants waster are the examples of biomass.  Gobar gas or bio-gas is the example of a bio - mass energy source.  Main constituent of a biogas or gobar gas is a methane gas.  Biogas plant is of two types: (a) Fixed-dome type, (b) Floating gas holder type.  Kinetic energy of wind is known as wind energy.  Wind energy is used to produce electricity.  The region where large number of wind mills are erected to produce electricity is called wind energy farm.  The minimum speed of wind to operate generator to produce electricity is about 15 km/h.  Constant and rapid use of conventional sources of energy would ultimately exhaust these sources and hence a need for tapping energy from alternate or non-conventional sources of energy is seriously felt.  Solar energy is the energy emitted by the sun in the form of heat and light.  Solar constant is defined as the energy received from the sun in one second by a unit square metre area of the outer edge of earth's atmosphere exposed perpendicular to the radiation of the sun at an average distance between the sun and the earth.  Value of solar constant = 1.4 k W/m2.  Solar devices like solar cooker, solar furnace, solar water heater, solar panels and solar cells are used to harness solar energy.  Water due to its high specific heat capacity (4200 J kg–1°C–1) is a store house of heat energy.  Energy from sea or ocean water is available in the form of (i) energy of sea waves (ii) Tidal energy and (iii) Ocean thermal energy (OTE).  The heat energy obtained from the conversion of nuclear mass is known as nuclear energy.  Nuclear energy is obtained by two processes known as nuclear fission and nuclear fusion.  Nuclear energy is expressed in electron - volt(eV) 1 eV = 1.6  10–19J 1 MeV = 106 eV = 1.6 –13J  Nuclear Fission is the process of splitting a heavy nucleus (say Uranium) into two comparatively lower nuclei along with the release of large amount energy when bombarded with thermal neutron.  Nuclear reactor is a device used to carry out controlled chain reaction.  Nuclear fusion is the process of fusing or combining together two small nuclei to form a comparatively big nucleus with the release of large energy.  Nuclear fusion reactions occur at very high temperature (107K).  Nuclear fusion reactions occurring in the interior of the sun are responsible for the energy of the sun. In other words, nuclear fusion reactions are the sources of energy of the sun.  Sources of energy are classified into two categories (i) conventional or non-renewable sources of energy and (ii) Non-conventional or renewable sources of energy.  Extraction and transportation of energy from various sources of energy cause environmental pollution.  The energy from various sources of energy must be used effectively to conserve energy.

 Energy is the essential requirement for each and every activity in our life.  The various sources of energy are the sun, the wind, water, fossil fuels etc.  The sun is the ultimate source of all forms of energy.  A good source of energy is one which supplies large amount of useful energy, easily available, economical and cause minimum environmental pollution. .  Thermal power plant generates electricity by burning fossil fuel like coal and oil.  LPG is a petroleum gas liquefied under pressure. Its full form is liquefied Petroleum Gas.  CNG is compressed Natural Gas.  Main constituents of CNG is methane.  Electricity produced by flowing water is known as hydro - electric power.  A plant used to produce hydro -electric power is known as hydro -electric power plant.  Potential energy of water stored in a dam is converted into kinetic energy of the falling water. This kinetic energy of falling water is converted into the kinetic energy of the armature of the generator which in turn is converted into electric energy.  Biomass is material which contains carbon and other combustible material.  Plants, wood animals and plants waster are the examples of biomass.  Gobar gas or bio-gas is the example of a bio - mass energy source.  Main constituent of a biogas or gobar gas is a methane gas.  Biogas plant is of two types: (a) Fixed-dome type, (b) Floating gas holder type.  Kinetic energy of wind is known as wind energy.  Wind energy is used to produce electricity.  The region where large number of wind mills are erected to produce electricity is called wind energy farm.  The minimum speed of wind to operate generator to produce electricity is about 15 km/h.  Constant and rapid use of conventional sources of energy would ultimately exhaust these sources and hence a need for tapping energy from alternate or non-conventional sources of energy is seriously felt.  Solar energy is the energy emitted by the sun in the form of heat and light.  Solar constant is defined as the energy received from the sun in one second by a unit square metre area of the outer edge of earth's atmosphere exposed perpendicular to the radiation of the sun at an average distance between the sun and the earth.  Value of solar constant = 1.4 k W/m2.  Solar devices like solar cooker, solar furnace, solar water heater, solar panels and solar cells are used to harness solar energy.  Water due to its high specific heat capacity (4200 J kg–1°C–1) is a store house of heat energy.  Energy from sea or ocean water is available in the form of (i) energy of sea waves (ii) Tidal energy and (iii) Ocean thermal energy (OTE).  The heat energy obtained from the conversion of nuclear mass is known as nuclear energy.  Nuclear energy is obtained by two processes known as nuclear fission and nuclear fusion.  Nuclear energy is expressed in electron - volt(eV) 1 eV = 1.6  10–19J 1 MeV = 106 eV = 1.6 –13J  Nuclear Fission is the process of splitting a heavy nucleus (say Uranium) into two comparatively lower nuclei along with the release of large amount energy when bombarded with thermal neutron.  Nuclear reactor is a device used to carry out controlled chain reaction.  Nuclear fusion is the process of fusing or combining together two small nuclei to form a comparatively big nucleus with the release of large energy.  Nuclear fusion reactions occur at very high temperature (107K).  Nuclear fusion reactions occurring in the interior of the sun are responsible for the energy of the sun. In other words, nuclear fusion reactions are the sources of energy of the sun.  Sources of energy are classified into two categories (i) conventional or non-renewable sources of energy and (ii) Non-conventional or renewable sources of energy.  Extraction and transportation of energy from various sources of energy cause environmental pollution.  The energy from various sources of energy must be used effectively to conserve energy.