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points in phase. Unit=m Amplitude Distance between rest position and crest or trough of wave. Amplitude represents the carrying energy of wave. Unit=m Compressions : These are high pressure regions on a pressure wave( longitudinal wave) Rarefactions: These are low pressure regions on a pressure wave (longitudinal wave) Analogue signal Continuous range of signal. Represented by sine wave Digital signal Discreet signals, only two values. Represented by square wave LIGHT Reflection Reflection of wave is bouncing back of wave, wave strike the obstacle, so it reflect to cause the direction changed, but the speed, wavelength and frequency are constant. Law of reflection | Angle of incidence is equal to the angle of reflection i=r Incident ray, reflected ray and normal line lie in same plane. Refraction Refraction of wave is the bending of wave, wave travel from one medium to other medium, so the speed and wavelength changed but constant frequency. Snell's law Ratio of sin of incident angle and sin of refracted = Bint angle isa constant (refractive index) eee Diffraction Diffraction of wave is the spreading out of wave when it passes through the gap or obstacle, so the speed, wavelength and frequency of wave are constant, shape changes. Angle of Itis the angle between the incident ray and the incidence normal. Angle of It is the angle between the reflected ray and the reflection normal. Angle of It is the angle between the refracted ray and the refraction normal. Normal Anormal is a perpendicular line drawn to a surface, at the exact point where the incident ray hits the surface Critical angle (c) Critical angle is that angle of incidence, for which n=1/sine the angle of refraction is 90° Total internal reflection Total internal reflection is when all light rays are only totally internally reflected. This happens when the angle of incidence is greater than the critical angle. It happen when the wave travel from denser medium to less dense medium. Optical fiber An optical fibre is a fibre that is made of silica or plastic, with a diameter just slightly greater than a human hair, Itis by nature flexible and transparent Refractive index Refractive index is a measure of the bending of light ray when light changes medium. It is the ratio of the velocity of light in a vacuum to its velocity ina specified medium. Refractive index is inversely proportional to wavelength of wave. n=c/v sind n=— sin n=1/sinc Converging lens A converging lens is a lens that allows all the parallel rays of light passing through it, toconverge ata point. Diverging lens: A diverging lens is a lens that causes the parallel rays of light incident on it to diverge and forma virtual image. Virtual image: Virtual image is the image that cannot be projected on the screen, A virtual image is an image formed by rays of light that do not actually meet to form that image. A virtual image is formed when diverging rays are extrapolated backwards and does not forma visible projection ona screen Real image: Areal image is an image formed by rays of light actually meeting at a point to form that image. Is the image that can projected on screen. Principal axis Imaginary line that connects optical center and principal focus of a lens Optical center(O) Center of the lens Focal length(f) Focal length of lens is the distance between the principle focal point and the centre of lens. (OF) Principle focus(F) Principle focus of lens is a point, after passing through lens, alll parallel light rays meet together. Dispersion of light The splitting of white light into its colours when it is incident on a prism due to refraction, is called as dispersion of light Spectrum: A band of colours formed as a result of dispersion is called as a spectrum, Monochromatic light: The visible light of a single frequency is described as monochromatic. Electromagnetic spectrum An electromagnetic spectrum consists of a range of all types of electromagnetic radiations. compounds is called as the chemical energy. Electrostatic It refers to the potential energy of a system of energy separated electric charges Elastic (Strain Strain energy is the energy stored in an object due to energy) its deformation. Internal The energy of a thermodynamic system is its (Thermal) energy _—_ internal energy. It is the energy associated with the random, disordered motion of molecules Elastic potential Energy store in the object due to change in shape. energy Conservation of Energy cannot be created and destroyed but it can energy transfer from one form to another forms. Efficiency Ratio of useful power/energy output over the total |. is powers energy input. : Newton's second It states that, for a body of constant mass "m" and Fema law: net force "F", we can state that F = ma, where F ( net force) and a (acceleration)/ Both are vector quantities. Friction: Friction is the force between two surfaces that may resist motion and produce heating, Drag force It is force acting in a direction that is opposite to the relative motion of the object moving with respect to the surrounding fluid. Fluid refers to liquids and __gases Momentum The product of mass and the velocity. Amount of p= mv motion in a body Unit= kgm/s Force Is the rate of change in the momentum f= ap t Principle of Total momentum before collision is equal to the momentum total momentum after collision without the external force act on the system Impulse Change in momentum OR the product of force and 1=Ap=Ft time duration of collision Unit= kgm/s Moment or Turning | The product of force and perpendicular distance Imoment= Fd effect of Force from pivot. Unit= Nm Principle of The total anti clockwise momentis equal tothe total F, dy= Fz dz moment clockwise moment about the pivot. Condition for equilibrium 1. No resultant force (resultant force=0) 2. No resultant moment(resultant moment=0) Centre of gravity Centre of gravity is the single point which whole weight of object act Centre of mass Centre of mass is the single point which whole mass is concentrated IGCSE PHYSICS DEFINITION NAME DEFINITION Formula Density Mass per unit volume. Unit= kg/m! p== Scalar Quantity that has only magnitude (size). Example, distance, speed, mass Vector Quantity that has both magnitude and direction. Example, displacement, velocity, force, weight, momentum Speed. Rate of change in distance unit: Ved/t Unit = m/s Velocity Rate of change in displacement. Ved/t Unit= m/s Acceleration Rate of change in velocity a=(v-u)/t Unit= m/s* Deceleration Negative acceleration or decrease in velocity m/s? Rate of change of velocity. Average speed Total distance / Total time Unit= m/s Stopping distance Distance covered when driver think about applying brakes till car is stopped. Stopping =thinking distance + braking distance Thinking distance Distance travelled in the time it takes the driver to react. (reaction time of driver) Braking distance The distance travelled when brakes are applied till car is stopped. Gravitational Force of gravity per unit mass. field strength Unit= m/s? OR N/kg Free fall Motion under only gravitational force and no air resistance, so constant acceleration as 9.8 m/s2 Weight Force due to gravitational field, so itis the productof w=mg mass and acceleration due to gravity (9.8m/s*). Work done Product of force and distance moved in direction of W= Fd force. OR change in energy. WeAE Unit= Joules or Nm One Joule: One Joule refers to the work done by a force of 1 Newton, when it displaces a body through 1m in the J=Nm direction of the farce applied Renewable ‘Type of energy that never runs out. Easily energy replenished. Energy from the sun, wind, ete. resources: Non-renewable Type of energy that runs out. Not easily replenished. energy: Energy from fossil fuels, natural gas Kinetic energy Energy due to movement. Unit= | Kes! mv? Gravitational Energy store in the object dueto change inheightin | GPE=imgh potential energy gravitational field energy Chemical energy The energy stored in the bonds of chemical Sun The Sun is avery bright, luminous, celestial anda stable star, situated in the spiral arm of the Milky Way galaxy and at the centre of the Solar System. Galaxy The word galaxy encompasses billions of stars along with their solar systems,gas and dust held by their gravity. There are more than a hundred billion galaxies in the universe. Milky way Milky way is a spiral galaxy that includes our solar system. It has billions of stars, including our Sun. Diameter of milky way= 1 * 10*5 light year Light-year: One light-year is the distance traveled by light in one year in space, Alight year= 9.5 * 10m Supernova Supernova isa powerful and luminous stellar explosion, that happens when a star has reached the end of its life.Example: Kepler's Supernova Nebula Nebula is a Latin word for fog or cloud.It consists of interstellar clouds consisting of Helium, Cosmic Dust, ionised gases, hydrogen as well as molecular clouds. [There are in all 5 different types of Nebulae, namely;emission nebulae, reflection nebulae, dark nebulae, planetary nebulae, and supernova remnants, Black hole A black hole is a region in the space, in which the effect of gravity is so strong, that it lets nothing escape out fit, not even light. The region appears to be black and circular.[ There are approximately 100 billion super massive black holes] Redshift Redshift is a phenomenon in which the spectrum of an astronomical abject gets displaced towards the longer( red) wavelength. Cosmic microwave background radiation (CMBR): Cosmic microwave background radiation (CMBR) is the leftover of the cosmic radiation after the big bang. Hubble constant Ho Hubble constant is the ratio of the speed at which the galaxy is moving away from the Earth to its distance from the Earth Ho=w/d Unit: 51 Average orbital speed v= 2(pi)R /T where r is the average radius of the orbit and T is the orbital period m/s or Km/h Solar system Solar system isa single term that includes eight planets and their moons in orbit round the sun. Also included in the solar systemare the smaller bodies such as the comets, asteroids, and the meteoroids. Orbital distance Orbital distance is the term that tells us the time taken by one object to revolve around the other. Orbital duration( Orbital time) Orbital duration is the time taken by one abject ta completely orbit around the other. Circular motion: Circular motion is the movement ofan object along the circumference of a circle or the rotation of an object along a circular path. Centripetal force = my? r Pressure Force per unit area. = Unit= Pascal ( Pa= N/m?) pen THERMAL Brownian Itis the random movement of larger particles, due to motion: their collision with faster moving, smaller particles. Absolute scale of temperature: Absolute zero Absolute zero is the temperature at which molecules has the lowest energy. This temperature corresponds to -273.15 °C (0K) oma Celsius temperature scale. Lowest possible temperature. State Boyle's law: For a fixed mass of a gas at constant temperature, PV= constant the volume varies inversely as the pressure. PAVi=P2V2 Thermal Thermal expansion is the expansion of an object expansion: under the influence of heat Melting point It is the temperature at which a solid changes into a liquid Boiling point Itis the temperature at which a liquid changes into a gas, without a rise in temperature. Evaporation: Itis the temperature at which a liquid changes into a gas, over a range of temperatures Good thermal Substances that allow the heat energy to flow conductors through them easily are called as good thermal conductors. They have free electrons Bad thermal Substances that do not allow the heat energy to ow conductors through them easily are called as good thermal (thermal insulators. They don’t have free elcetrons insulators); Specific heat Heat energy that is required to change the E=mcAT capacity temperature 1 Celsius for 1 kg of mass. Unit: | /kgC or _I/kek Thermal capacity | Is the heat energy per unit temperature that require | E=cAT to change temperature 1 Celsius Unit: ]/C or Conduction Transfer of energy through the movement of particles. By free electrons, by vibration of lattice, electrons hitting molecules and transferring energy. Convection: Convection isa process of heat transfer involving density differences within molecules of the same fluid , in which the warmer and less dense portions rise up, while the more dense and the heavier ones sink down. Radiation Transferring of heat by infrared radiation. Radiation refers to the process of transmission or emission of energy in the form of waves that can travel through vacuum, meaning they do not require any medium. Hooke’s law Extension in the spring is directly proportion to the force/load applied, within the limit of propotonality. F=kx x=l-lo Proportional limit Final point that the object will obey Hooke's law. Elastic limit Is the point where is the maximum extent to which an object can stretch without the permanent deformation and when it beyond elastic limit, it cannot return to original shape when removed force. Spring constant Force per unit extension. K=F/x Unit depends on unit of Fand x Spring constant tells us how hard the springis. WAVES Wave motion: Wave motion is the transfer of energy from one place to another, without transferring matter. Wave front: Wave front is the imaginary line joining all the crests ona wave. Transverse wave A transverse wave is a wave in which the direction of vibration of particles is at perpendicular to the direction of propagation. They have crest and trough. Examples include: electromagnetic radiation, water waves and seismic S-waves (secondary). Longitudinal wave Fora longitudinal wave, the direction of vibration of particles is parallel to the direction of propagation. ‘They have compression and rarefaction. Examples, sound waves and seismic P-waves (primary). Time Period(T) Time taken for ONE complete oscillation. Frequency(f) Number of oscillation per second. Frequency is the number of vibrations passing through a point per unit time. Wavelength(®) Wavelength is the distance between two consecutive crests, two consecutive troughs or between any two vefa 
