IMPORTANT FORMULAS

• Maximum number of electrons that can be accommodated in a shell = 2n²
  where 'n' is the number of the given shell from the nucleus.


• MIRROR FORMULA:
  
  (1/v) + (1/u) = (1/f) = (2/R)
  
  Where u, v, f and R are object distance, image distance, focal length of mirror and radius of curvature of mirror, respectively.


• LENS FORMULA:
  
  (1/v) - (1/u) = (1/f)
  
  Where u, v and f are object distance, image distance and focal length of lens, respectively.


• MAGNIFICATION:
  
  m = (h'/h) = (-v/u) for mirror
  
  m = (h'/h) = (v/u) for lens
  
  Where m, h' and h are magnification, image height and object height, respectively.


• η₂₁ = (sin i/sin r)
  
  Where η₂₁, i and r are refractive index of medium 2 with respect to medium 1, angle of incidence and angle of refraction, respectively.


• η₂₁ = (v₁/v₂)
  
  Where η₂₁, v₁ and v₂ are refractive index of medium 2 with respect to medium 1, speed of light in medium 1 and speed of light in medium 2, respectively.


• η_m = (c/v)
  
  Where η_m, c and v are absolute refractive index of a medium, speed of light in vacuum and speed of light in the medium, respectively.


• P = (1/f)
  
  Where P and f are power of lens in dioptre and focal length of lens in metre, respectively.


• I =(Q/t)
  
  Where I, Q and t are current in ampere, charge in coulomb and time in seconds, respectively.


• V = (W/Q)
  
  Where V, W and Q are voltage(potential difference) in volt, work done in joule and charge in coulomb, respectively.


• V = IR
  
  Where V, I and R are voltage in volt, current in ampere and resistance in ohm, respectively.


• R = ρ(l/A)
  
  Where R, ρ, l and A are resistance in ohm, resistivity in ohm-meter, length of the conductor in meter and cross-sectional area of conductor in m², respectively.


• R = R₁ + R₂ + R₃ +....
  
  Where R is the equivalent resistance of R₁, R₂, R₃,...connected in series.


• R = (1/R₁) + (1/R₂) + (1/R₃) +....
  
  Where R is the equivalent resistance of R₁, R₂, R₃,...connected in parallel.


• H = VIt = I²Rt
  
  Where H, V, I, R and t are heat produced in joule, voltage in volt, current in ampere, resistance in ohm and time in second, respectively.


• P = VI = I²R = (V²/R)
  
  Where P, V, I and R are power in watt, voltage in volt, current in ampere and resistance in ohm, respectively.


• 1 kWh = 3.6 x 10⁶ joule
  
  [kWh is kilowatthour also called 'unit' of electrical energy]

IMPORTANT LAWS

1. Law of Conservation of Mass : Mass can neither be created nor be destroyed, i.e. the total mass in a closed system remains unchanged.


2. Dobereiner's Law of Triads : When three elements with similar properties are arranged in the order of increasing atomic masses, the atomic mass of the middle element is roughly the average of the atomic masses of the other two elements.


3. Newland's Law of Octaves : If the elements are arranged in the order of increasing atomic mass, a similar set of properties is observed in every eighth element.


4. Mendeleev's Periodic Law : The properties of elements are the periodic function of their atomic masses.


5. Modern Periodic Law : The properties of elements are the periodic function of their atomic number.


6. Laws of Reflection :
   • The angle of incidence is always equal to the angle of reflection.
   • The incident ray, the normal to the reflecting surface at the point of incidence and the reflected ray, all lie in the same plane.


7. Laws of Refraction :
   • The incident ray, the refracted ray and the normal to the surface separating the two mediums at the point of incidence, all lie in the same plane.
   • The ratio of the sine of angle of incidence to the sine of angle of refraction is a constant, for the light of given colour and for the given pair of mediums.(better known as Snell's law)


8. Ohm's Law : The electric current flowing through a conducting wire is directly proportional to the potential difference across its terminals provided its temperature remains the same.


9. Joule's Law of Heating : The heat produced in a resistor is (i) directly proportional to the square of the current for a given resistance, (ii) directly proportional to the resistance for a given current, and (iii) directly proportional to the time for which the current flows through the resistor.


10. Right-Hand Thumb Rule : Hold (imagine to hold) a current-carrying straight conductor in your right hand such that the thumb points towards the direction of current, then the fingers would wrap around the conductor in the direction of the field lines of the magnetic field.


11. Maxwell's Cork-Screw Rule : If we consider ourselves driving a cork-screw in the direction of the current, then the direction of the cork-screw is the direction of the magnetic field.


12. Fleming's Left-Hand Rule : Stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.


13. Fleming's Right-Hand Rule : Stretch the thumb, forefinger and middle finger of your right hand such that they are mutually perpendicular. If the forefinger indicates the direction of the magnetic field and the thumb shows the direction of motion of the conductor, then the middle finger will show the direction of the induced current.


14. Law of Conservation of Energy : Energy can neither be created nor be destroyed,i.e. total energy of a closed system remains unchanged.


15. 10% Law : About 10% of the available chemical energy of one trophic level of a food-chain is transferred to the next higher trophic level.

DEFINITIONS : BIOLOGY

1. LIFE PROCESSES: The processes occurring in the body of living organisms so as to maintain it are called Life Processes.


2. FOOD: A useful source of both energy and structural material to the body of an organism for growth and maintenance is called Food.


3. NUTRITION: The process of providing nutrients to the body from outside sources consumed as food is called Nutrition.


4. RESPIRATION: The process of acquiring oxygen from an external source and using it for the process of breakdown of food material for cellular needs is called Respiration.


5. BREATHING: The mechanical process of inhalation of oxygen-rich air from the environment and exhalation of oxygen-deficient(deoxygenated) air from the body alternatively is called Breathing.


6. EXCRETION: The process of removal from the body of waste by-products generated during various metabolic processes is called Excretion.


7. AUTOTROPHS: Those organisms which can prepare their own food from inorganic materials obtained from the nature are called Autotrophs.


8. HETEROTROPHS: Those organisms which cannot prepare their own food but obtain it from other living organisms are called Heterotrophs.


9. ENZYMES: Enzymes are biochemical catalysts which help in breaking down of complex food molecules in to simpler ones.


10. PHOTOSYNTHESIS: The process used by autotrophs in which they prepare complex organic molecules from simple inorganic molecules like carbon dioxide and water using sun's energy is called Photosynthesis.


11. ANAEROBIC RESPIRATION: The process of respiration taking place in absence of air(oxygen) is called Anaerobic respiration.


12. AEROBIC RESPIRATION: The process of respiration taking place in presence of air(oxygen) is called Aerobic respiration.


13. TRANSPORTATION: The process of transfer of various materials like food, carbon dioxide, metabolic wastes, hormones, etc. from one organ to another in the body is called Transportation.


14. ARTERY: The blood vessel carrying blood from heart to other organs of the body is called Artery.


15. VEIN: The blood vessel carrying blood from different organs of the body to heart is called vein.


16. TRANSPIRATION: The loss of water in the form of vapour from the aerial parts of the plant is called Transpiration.


17. TRANSLOCATION: The transport of products of photosynthesis (food) from leaves to the other parts of the plant is called Translocation.


18. COORDINATION: The working together of different systems in the body so that the body acts as a harmonious (whole) unit is called Coordination.


19. REFLEX ACTION: A sudden unconscious and involuntary (automatic) response of effectors to the stimulus is called Reflex action.


20. REFLEX ARC: The pathway, involving the effector organ, sensory nerve, spinal cord and motor nerve, through which reflex action is performed is called Reflex Arc.


21. CENTRAL NERVOUS SYSTEM: The nervous system formed by the brain and the spinal cord is called the Central Nervous System.


22. Neuron: Neuron is the structural and functional unit of nervous system


23. SENSORY NEURON: The neuron which conveys an impulse(message) from an organ to the brain or spinal cord is called Sensory Neuron.


24. MOTOR NEURONE: The neuron which conveys a message from brain or spinal cord to the effector organ is called Motor Neuron.


25. SYNAPSE: The junction between the axon of one neuron and the dendrite of another neuron through which an impulse is transmitted between two neurons is called a Synapse.


26. STIMULUS: An external factor (environmental factor) to which an organism responds is called a Stimulus.


27. TROPISM: The directional growth of a plant in response to a stimulus is called Tropism.


28. PHOTOTROPISM: The directional growth (response) of a plant towards light is called Phototropism.


29. GEOTROPISM(GRAVITOTROPISM): The directional growth of a plant in the direction of gravitation or against it is called Geotropism.


30. HYDROTROPISM: The directional growth of a plant (roots) towards water is called Hydrotropism.


31. CHEMOTROPISM: The directional growth of a plant organ towards specific chemicals is called Chemotropism.


32. REPRODUCTION: A process by which living organisms produce organisms similar to them is called Reproduction.


33. VARIATION: The difference between individuals of the same species and the progeny of same parents is called Variation.


34. FISSION: The breaking of an unicellular organism after growth in two or more parts each of which then behaves as an individual organism is called Fission.


35. BINARY FISSION: The breaking of an organism into two exactly similar organisms which then grow and live as an independent organism is called Binary fission.


36. MULTIPLE FISSION: The breaking of an organism into several similar organisms each of which then behaves as an independent organism is called Multiple Fission.


37. FRAGMENTATION: The breaking up of a multicellular organism into smaller pieces and the development of an independent organism from each of these pieces is called Fragmentation.


38. REGENERATION: The capability of an organism to give rise to new individual organisms from their body parts whereby each part develops into a new organism is called Regeneration.


39. BUDDING: The formation of a bud-like structure on the body of an organism which grows as exact replica of the parent organism and then gets detached from it to behave as an independent organism is called Budding.


40. VEGETATIVE PROPAGATION: The development of a new plant from parts of root, stem, or leaves under appropriate conditions is called Vegetative Propagation.


41. ASEXUAL REPRODUCTION: The method of reproduction in which fusion of two gamates is not involved, i.e. the development of a new organism does not require two parents, is called Asexual Reproduction.


42. SEXUAL REPRODUCTION: The method of reproduction in which the fusion of a male gamate and a female gamate results in the development of a new organism is called Sexual Reproduction.


43. UNISEXUAL ORGANISM: An organism which possesses either the male sex organ or the female sex organ is called Unisexual organism.


44. BISEXUAL ORGANISM: An organism which possesses both male and female sex organs is called Bisexual organism.


45. FERTILISATION: The fusion of a male gamate with a female gamate resulting in the formation of a zygote is called Fertilisation.


46. GERMINATION: The development of a seedling from the seed under appropriate conditions is called Germination.


47. ZYGOTE: The diploid gamete formed by the fusion of a male gamete with a female gamete is called a Zygote.


48. GAMETE: A gamete is a haploid sex cell, either a sperm or an ovum, containing half number of chromosomes.


49. PUBERTY: The stage of the life of a human being at which the sexual organs become functional along with certain characteristic changes in body, voice, behaviour,etc.


50. MENSTRUAL CYCLE: The sexual cycle in a female which is repeated periodically every month and involves a series of phenomena from ovulation to the discharge of unfertilised egg with blood from vagina is called Menstrual Cycle.


51. MENSTRUATION: The periodic discharge of unfertilised ovum along with disintegrated tissues of uterus wall and blood, which lasts for about 3-5 days, is called Menstruation.


52. REPRODUCTIVE HEALTH: Prevention of diseases occurring through reproductive system and sexual contact by proper measures and cleanliness to maintain healthy state of the body is called Reproductive Health.


53. HEREDITY: The transmission of certain biological characteristics from parents to the offspring is called Heredity.


54. GENETICS: The branch of science which deals with heredity and variation in organisms is called Genetics.


55. EVOLUTION: The gradual cumulative change in the characteristics of organisms of the related species over a long period of time (over many generations) is called Evolution.


56. SPECIATION: Speciation is a process by which new species of organisms arise from the existing ones.


57. INHERITED TRAIT: A characteristic of an organism induced by a change in its genes is called an Inherited Trait.


58. ACQUIRED TRAIT: A characteristic of an organism which develops as a response to the environmental change and which is not inherited one is called an Acquired Trait.


59. HOMOLOGOUS ORGANS: The organs showing similarities in origin but performing different functions (in different organisms) are called Homologous Organs.


60. ANALOGOUS ORGANS: The organs showing different origin but performing similar functions (in different organisms) are called Analogous organs.


61. FOSSILS: Remains (or impressions), of once living organisms, which have been preserved within the layers of rocks over the years are called Fossils.


62. POLLINATION: The transfer of ripe pollen from an anther to the stigma of a flower of the same species is called Pollination.


63. SELF-POLLINATION: When pollen is carried from an anther to the stigma of the same flower or another flower on the same plant, it is called Self-pollination.


64. CROSS-POLLINATION: When the pollen is transferred from a flower of one plant to a flower of another plant of the same species, it is called Cross-pollination.


65. ENVIRONMENT: The physical surroundings and living organisms with which an organism interacts is called Environment.


66. BIODEGRADATION: The breaking down of substances into simpler molecules by the activity of micro-organisms is called Biodegradation.


67. ECOSYSTEM: A community of interdependent organisms together with the environment they inhabit and with which they interact is called an Ecosystem.


68. PRODUCERS: The organisms which produce food from natural simple inorganic molecules and trap sun's energy in it are called Producers.


69. CONSUMERS: The organisms which utilise food and energy from the preceding trophic level (either a producer or itself a consumer) are called Consumers.


70. Decomposers: The organisms which decompose organic waste materials and dead bodies of organisms into simpler substances are called Decomposers.


71. FOOD CHAIN: A series of organisms which are interlinked with one another for their requirements of food and energy is called a Food chain.


72. FOOD WEB: A complex network of many interlinked food chains is called a Food web.


73. BIOMAGNIFICATION (BIOLOGICAL MAGNIFICATION): The accumulation of non-biodegradable pollutants in the organisms of a food chain so that at each successive trophic level the amount of the substance relative to the biomass is increased is called Biomagnification.


74. BIODIVERSITY: The existence of organisms of different species as well as different organisms of same species in an ecosystem is called Biodiversity.


75. WILDLIFE: A combination of organisms, both plants and animals, which forms the population of a forest ecosystem is called Wildlife.

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.

DEFINITIONS : CHEMISTRY

• Chemical Reaction: When a substance changes chemically during a reaction, the reaction is called a chemical reaction.


• Reactant: The substance that undergoes chemical change is called a reactant.


• Product: The new substance that is formed during a reaction is called a product.


• Skeletal Chemical Equation: A chemical equation which shows both reactants and products but which is not balanced as regards the mass of the substances involved is called a skeletal chemical equation.


• Combination Reaction: A reaction in which a single product is formed from two or more reactants is called a Combination reaction.


• Exothermic Reaction: A reaction in which heat is evolved along with the formation of the products is called an Exothermic reaction.


• Endothermic Reaction: A reaction in which heat is absorbed during the formation of products is called an Endothermic reaction.


• Decomposition Reaction: A reaction in which a single reactant breaks down to give more than one simpler product is called a Decomposition reaction.


• Thermal Decomposition: A reaction in which decomposition of reactant is carried out by heating it is called thermal decomposition.


• Displacement Reaction: A reaction in which a more reactive element displaces a less reactive element from its solution is called a displacement reaction.


• Double Displacement Reaction: A reaction which involves an exchange of ions between the reactants is called a double displacement reaction.


• Precipitation Reaction: A reaction in which an insoluble product(precipitate) is formed is called a precipitation reaction.


• Oxidation: If a substance gains oxygen or loses hydrogen it is said to undergo oxidation.


• Reduction: If a substance gains hydrogen or loses oxygen it is said to undergo reduction.


• Redox Reaction: A reaction in which one substance is oxidised and the other is reduced is called Redox reaction.[NOTE: A reaction cannot be either an oxidation reaction or a reduction reaction independently.]


• Corrosion: When a metal is attacked by substances like moisture, acids, etc. around it and converted into its salt it is said to corrode and the process is called corrosion.


• Rancidity: The change in the smell and taste of fats and oils due to their oxidation is called rancidity.


• Olfactory Indicators: Substances whose odour changes in acidic or basic mediums are called olfactory indicators when they are used to identify whether a substance is an acid or a base.


• Neutralisation Reaction: The reaction between an acid and a base giving a salt and water is called neutralisation reaction.


• Alkali: Bases which are soluble in water are called alkalies.


• Antacid: A base which is used to neutralise excess hydrochloric acid produced in stomach to reduce pain and irritation is called an antacid.


• Water of Crystallisation: The fixed number of water molecules present in one formula unit of a salt(compound) is called water of crystallisation.


• Ductility: The ability of metals to be drawn into thin wires is called ductility.


• Malleability: The ability of metals to be beaten(hammered) inti thin sheets is called malleability.


• Allotrope: Each of structurally different forms of an element is called an allotrope of that element.


• Ionic Compounds: Compounds formed by the transfer of electrons from a metal to a nonmetal are called ionic compounds.


• Covalent Compounds: Compounds formed by sharing of electron pairs between atoms are called covalent compounds.


• Minerals: The elements or compounds which occur naturally in the earth's crust are called minerals.[NOTE: Minerals in chemistry are compounds in general but Minerals in biology are elements. For example Na and Fe are minerals for a biologist]


• Ore: A mineral from which a particular metal can be extracted profitably is called an ore.


• Gangue: Impurities like sand present in an ore mined from the earth are collectively called gangue.


• Calcination: The process of heating carbonate ores strongly in limited supply of air to change them into oxides is called calcination.


• Roasting: The process of heating sulphide ores strongly in presence of excessive air to change them into oxides is called roasting.


• Galvanisation: The process of deposition(coating) of a thin layer of zinc on steel and iron to prevent their rusting is called galvanisation.


• Alloy: A homogeneous mixture of two or more metals or a metal and a nonmetal is called an alloy.


• Amalgam: An alloy containing mercury as one of the constituents is called an amalgam.


• Catenation: The property of carbon atoms by which one carbon atom can form covalent bonds with other carbon atoms giving rise to large molecules is called catenation.


• Isomers: Compounds with identical molecular formula but different structures(atomic arrangements) are called isomers.


• Functional Group: An atom or a group of atoms which confers specific properties to an organic compound regardless of the length and nature of the carbon chain is called a functional group.


• Homologous Series: A series of organic compounds having same functional group and in which there is a difference of -CH₂ between two successive compounds is called homologous series.


• Addition Reaction: A reaction in which an atom or group of atoms enters a molecule without replacing another atom from it is called an addition reaction.


• Substitution Reaction: A reaction in which an atom or group of atoms replaces another atom(or group of atoms) to enter the molecule is called a substitution reaction.


• Catalyst: A catalyst is a substance that causes a reaction to occur or proceed at a different rate without the reaction itself being affected.


• Isotope: Isotopes are atoms of an element with similar chemical properties but different atomic masses due to different number of neutrons in their nuclei.


• Atomic Radius: The distance between the centre of the nucleus and the outermost shell of an isolated atom is called its atomic radius.


• Oxidising Agent: A substance which supplies oxygen to or removes hydrogen from other substance is called an oxidising agent.


• Reducing Agent: A substance which supplies hydrogen to or removes oxygen from other substance is called an reducing agent.

MY AIM

In very short time from now I am going to add useful notes with a very different approach on this site for the students of class 10 CBSE(INDIA). I will be writing the notes in the form of different posts as and when time permits. Students are requested to visit the blog time and again to find fresh material for their reference.