WORLD CRYPTO AND NET

✡️Notes on Atomic Physics✡️ e/m of an electron (Thomson Method):- (a) e/m of a particle is called the specific charge of the particle. e/m = v/rB Here, r is the radius of curvature, B is the strength of magnetic field, v is the velocity, e is the charge on cathode ray particle and m is the mass. (b) v = E/B Electric field:- E = V/d Photo electric effect:- Photo-electric effect is the phenomenon of emission of electrons from the surfaces of certain substances, mainly metals, when light of shorter wavelength is incident upon them. Effect of collector’s potential on photoelectric current:- (a) Presence of current for zero value potential indicates that the electrons are ejected from the surface of emitter with some energy. (b) A gradual change in the number of electrons reaching the collector due to change in its potential indicates that the electrons are ejected with a variety of velocities. (c) Current is reduced to zero for some negative potential of collector indicating that there is some upper limit to the energy of electrons emitted. (d) Current depends upon the intensity of incident light. (e) Stopping potential is independent of the intensity of light. Effect of intensity of light:- The photoelectric currentis directly proportional to theintensity of incident radiation. Effect of frequency of light:- (a) Stopping potentialdepends upon thefrequency of light. Greater the frequency of light greater is the stopping potential. (b) Saturation current is independent of frequency. (c) Threshold frequency is the minimum frequency, that capable of producing photoelectric effect. Laws of Photoelectricity:- (a) Photoelectric effect is an instantaneous process. (b) Photoelectric current is directly proportional to the intensity of incident light and is independent of its frequency. (c) The stopping potential and hence the maximum velocity of the electrons depends upon the frequency of incident light and is independent of its frequency. (d) The emission of electrons stops below a certain minimum frequency known as threshold frequency. Energy contained in bundle or packet:- E = hf = hc/λ Here h is the Planck’s constant and f is the frequency. Work function:- It is defined as the minimum energy required to pull an electron out from the surface of metal. It is denoted by W0. Einstein’s equation of photoelectric effect:- (a) ½ mvmax2 = hf – W0 (b) ½ mvmax2 = hf – hf0 = h(f- f0) = h [c/λ – c/λ0] (c) eV0 = hf - W0 (d)V0 = [(h/e)f] – [W0/e] Here f0 is threshold frequency. Threshold frequency (f0):- f0 = work function/h = W/h Maximum kinetic energy of emitted photo electrons:- ?Kmax= ½ mvmax2 = eV0 Threshold wavelength:- λ0 = c/f0 = hc/hf0 = hc/W Slope of V0~ v graph:- Slope= h/e Rest mass of photon = 0, Charge = 0 Energy of photon:- E = hf = hc/λ Momentum of photon:- p = E/c = h/λ = hf/c Mass od photon:- m = E/c2 = h/cλ = hf/c2 For electron, λe = [12.27/√V]Å For proton, λp = [0.286/√V]Å For alpha particle, λα = [0.286/√V]Å For particle at temperature T, λ = h/√3mKT (E = 3/2 KT) The wavelength of electron accelerated by potential difference of V volts is:- λe= [12.27/√V]Å Number of photons:- (a) Number of photons per sec per m2, np = Intensity/hf (b) Number of photons incident per second, np = Power/hf (c) Number of electrons emitted per second = (efficiency per surface)× (number of photons incident per second) Compton wave length:- (a) λc = h/m0c Here h is the Planck’s constant, m0 is the rest mass of electron and c is the speed of light. (b) Change in wavelength:- λ' – λ =λc (1-cos?) de Broglie wavelength (λ):-λ = h/mv = h/√(2mE) = h/√(2meV) In accordance to Bohr’s postulate of atomic structure, the angular momentum of an electron is an integral multiple of h/2π. So, mvr = nh/2π Bragg’s diffraction law:- 2dsinθ = nλ Here λ is the wavelength of electron and d is distance between the planes. Rutherford’s atomic model (α-particle scattering):- (a) N(θ) ∝ cosec4(θ/2) (b) Impact parameter, b = [(Ze2) (cot θ/2)]/[(4πε0)E] Here, E = ½ mv2 = KE of theα particle. @ET_STUDY_NOTES

✅ Atomic and Molecular Masses ➖Atomic Mass: Mass of an atom. Reported in atomic mass unit “amu” or unified mass “u” One atomic mass unit i.e. amu, is the mass exactly equal to one-twelfth the mass of one carbon-12 atom. ➖Molecular Mass: Mass of a molecule of covalent compound. It is equal to the sum of atomic masses of all the elements present in the molecule. Formula Unit Mass Mass of a molecule of an ionic compound It is also equal to the sum of atomic masses of all the elements present in the molecule ✅ Mole Concept: ➖Mole: Unit of amount of substance. One mole amount of substance that contains as many particles or entities as there are atoms in exactly 12 g of the 12C isotope. ➖Molar mass: Mass of one mole of a substance in gram Molar mass in gram in numerically equal to atomic/molecular/formula mass in amu or u. ▬▬▬▬▬▬▬▬▬▬▬▬▬ 📚JOIN: @Ethio_Educational_News 📚JOIN: @EUEE_TIPS 📚JOIN: @Et_Study_Notes

📚 Some Basic Concepts of Chemistry 📚 Matter: Anything that exhibits inertia is called matter. The quantity of matter is its mass. Classification of Matter:- Based on chemical composition of various substances. 📍Elements: ➖It is the simplest form of the matter. ➖Smallest unit of an element is known as atom. ➖Total number of the known elements is 118 out of which 98 elements occur naturally and 20 are formed by artificial transmutation. ➖Examples: Na, K, Mg. Al, Si, P, C, F, Br etc. 📍Compound: ➖It is a non-elemental pure compound. ➖Formed by chemical combination of two or more atoms of different elements in a fixed ratio. ➖Examples: H2O, CO2, C6H12O6 etc. 📍Mixture: ➖Formed by physical combination of two or more pure substances in any ratio. ➖Chemical identity of the pure components remains maintained in mixtures. ➖Homogeneous mixtures are those whose composition for each part remains constant. ➖Example, Aqueous and gaseous solution. ➖Heterogeneous mixtures are those whose composition may vary for each and every part. ➖Example, Soil and concrete mixtures. 🧩Dalton’s Atomic Theory: ➖Every matter consists of indivisible atoms. ➖Atoms can neither be created nor destroyed. ➖Atoms of a given element are identical in properties ➖ Atoms of different elements differ in properties. ➖Atoms of different elements combine in a fixed ratio to form molecule of a compound. 🧩Precision and Accuracy: ➖Precision: Closeness of outcomes of different measurements taken for the same quantity. ➖Accuracy: Agreement of experimental value to the true value 🧩Laws of Chemical Combination: ➖Law of conservation of mass: “For any chemical change total mass of active reactants are always equal to the mass of the product formed” ➖Law of constant proportions: “A chemical compound always contains same elements in definite proportion by mass and it does not depend on the source of compound”. ➖Law of multiple proportions: “When two elements combine to form two or more than two different compounds then the different masses of one element B which combine with fixed mass of the other element bear a simple ratio to one another” ➖Law of reciprocal proportion: “ If two elements B and C react with the same mass of a third element (A), the ratio in which they do so will be the same or simple multiple if B and C reacts with each other”. ➖Gay Lussac’s law of combining volumes: “At given temperature and pressure the volumes of all gaseous reactants and products bear a simple whole number ratio to each other”. ▬▬▬▬▬▬▬▬▬▬▬▬▬ 📚JOIN: @Ethio_Educational_News 📚JOIN: @EUEE_TIPS 📚JOIN: @Et_Study_Notes