Practice Questions

Q18.Following statements related to radioactivity are given below : (A) Radioactivity is a random and spontaneous process and is dependent on physical and chemical conditions. (B) The number of undecayed nuclei in the radioactive sample decays exponentially with time. (C) Slope of the graph of loge (no. of undecayed nuclei) vs. time represents the reciprocal of mean life time (τ) . 1 (D) Product of decay constant (λ) and half-life time (T 2 ) is not constant. Choose the most appropriate answer from the options given below: (1) (A) and (B) only (2) (B) and (D) only (3) (B) and (C) only (4) (C) and (D) only

Q18.Given below are two statements Statement I: In hydrogen atom, the frequency of radiation emitted when an electron jumps from lower energy orbit (E1) to higher energy orbit (E2), is given as hf = E1 −E2 Statement II: The jumping of electron from higher energy orbit (E2) to lower energy orbit (E1) is associated with frequency of radiation given as f = (E2−E1)h . This condition is Bohr's frequency condition. In the light of the above statements, choose the correct answer from the options given below: (1) Both statement I and statement II are true. (2) Both statement I and statement II are false. (3) Statement I is correct but statement II is false. (4) Statement I is incorrect but statement II is true.

Q18.A radioactive nucleus can decay by two different processes. Half-life for the first process is 3. 0 hours while it is 4. 5 hours for the second process. The effective halflife of the nucleus will be (1) 3. 75 hours (2) 0. 56 hours (3) 0. 26 hours (4) 1. 80 hours

Q18.An α particle and a carbon 12 atom has same kinetic energy K . The ratio of their de-Broglie wavelengths (λα : λC12) is (1) √3 : 1 (2) 1 : √3 (3) 2 : √3 (4) 3 : 1

Q18.An unpolarised light beam of intensity 2𝐼0 is passed through a polaroid 𝑃 and then through another polaroid 𝑄 which is oriented in such a way that its passing axis makes an angle of 30° relative to that of 𝑃. The intensity of the emergent light is (1) 𝐼0 (2) 𝐼0 4 2 3𝐼0 3𝐼0 (3) (4) 4 2 JEE Main 2022 (29 Jul Shift 2) JEE Main Previous Year Paper

Q18.A radioactive sample decays 7 times its original quantity in 15 minutes. The half-life of the sample is 8 (1) 5 min (2) 7. 5 min (3) 15 min (4) 30 min

Q18.Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : The photoelectric effect does not take place, if the energy of the incident radiation is less than the work function of a metal. Reason R : Kinetic energy of the photoelectrons is zero, if the energy of the incident radiation is equal to the work function of a metal. (1) Both A and R are correct and R is the correct (2) Both A and R are correct but R is not the correct explanation of A explanation of A (3) A is correct but R is not correct (4) A is not correct but R is correct

Q18.A metal exposed to light of wavelength 800 nm and emits photoelectrons with a certain kinetic energy. The maximum kinetic energy of photo-electron doubles when light of wavelength 500 nm is used. The work JEE Main 2022 (25 Jul Shift 1) JEE Main Previous Year Paper function of the metal is (Take ℎ𝑐= 1230 eV - nm). (1) 1 . 537eV (2) 2 . 46eV (3) 0 . 615eV (4) 1 . 23eV

Q18.The ratio of wavelengths of proton and deuteron accelerated by potential Vp and Vd is 1 : √2 . Then, the ratio of Vp to Vd will be (1) 1 : 1 (2) √2 : 1 (3) 2 : 1 (4) 4 : 1

Q18.The disintegration rate of a certain radioactive sample at any instant is 4250 disintegrations per minute. 10 minutes later, the rate becomes 2250 disintegrations per minute. The approximate decay constant is (Take loge 1. 88 = 0. 63 ) (1) 0. 02 min−1 (2) 2. 7 min−1 (3) 0. 063 min−1 (4) 6. 3 min−1

Q18.The activity of a radioactive material is 6. 4 × 10−4 curie. Its half life is 5 days. The activity will become 5 × 10−6 curie after (1) 7 days (2) 15 days (3) 25 days (4) 35 days JEE Main 2022 (27 Jul Shift 2) JEE Main Previous Year Paper

Q18.An electric bulb is rated as 200 W. What will be the peak magnetic field at 4 m distance produced by the radiations coming from this bulb? Consider this bulb as a point source with 3. 5% efficiency. (1) 1. 19 × 10−8T (2) 1. 71 × 10−8T (3) 0. 84 × 10−8T (4) 3. 36 × 10−8T

Q18.Mass numbers of two nuclei are in the ratio of 4: 3. Their nuclear densities will be in the ratio of (1) 4: 3 (2) 3 13 4 (3) 1: 1 (4) 4 13 3

Q19.In the given circuit the input voltage Vin is shown in figure. The cut-in voltage of p −n junction diode ( D1 or D2 ) is 0. 6 V . Which of the following output voltage (V0) waveform across the diode is correct? JEE Main 2022 (28 Jun Shift 2) JEE Main Previous Year Paper (1) (2) (3) (4)

Q19.Identify the logic operation performed by the given circuit (1) AND gate (2) OR gate (3) NOR gate (4) NAND gate

Q19.Given below are two statements : One is labelled as Assertion A and the other is labelled as Reason R. Assertion A : n −p −n transistor permits more current than a p −n −p transistor. Reason R : Electrons have greater mobility as a charge carrier. (1) Both A and R true, and R is correct explanation (2) Both A and R are true but R is NOT the correct of A. explanation of A. (3) A is true but R is false. (4) A is false but R is true.

Q19.In the following nuclear reaction, β− γ D α→D1 →D2 α→D3 →D4 Mass number of D is 182 and atomic number is 74 . Mass number and atomic number of D4 respectively will be (1) 174 and 71 (2) 174 and 69 (3) 172 and 69 (4) 172 and 71

Q19.For a constant collector-emitter voltage of 8 V , the collector current of a transistor reached to the value of 6 mA from 4 mA , whereas base current changed from 20 μA to 25 μA value. If transistor is in active state, small signal current gain (current amplification factor) will be (1) 240 (2) 400 (3) 0. 0025 (4) 200

Q19.Hydrogen atom from excited state comes to the ground by emitting a photon of wavelength λ. The value of principal quantum number n of the excited state will be : ( R : Rydberg constant) (1) √λRλ−1 (2) √ λR−1λR (3) √ λR−1λ (4) √λR2λR−1

Q19.A logic gate circuit has two inputs A and B and output Y . The voltage waveforms of A, B and Y are shown below The logic gate circuit is (1) AND gate (2) OR gate (3) NOR gate (4) NAND gate

Q19.A radio can tune to any station in 6 MHz to 10 MHz band. The value of corresponding wavelength bandwidth will be (1) 4 m (2) 20 m (3) 30 m (4) 50 m

Q19.The light of two different frequencies whose photons have energies 3. 8 eV and 1. 4 eV respectively, illuminate a metallic surface whose work function is 0. 6 eV successively. The ratio of maximum speeds of emitted electrons for the two frequencies respectively will be : (1) 2 : 1 (2) 4 : 1 (3) 1 : 2 (4) 1 : 4

Q19.Identify the solar cell characteristics from the following options : JEE Main 2022 (28 Jul Shift 1) JEE Main Previous Year Paper (1) (2) (3) (4)

Q19.The maximum and minimum voltage of an amplitude modulated signal are 60 V and 20 V respectively. The percentage modulation index will be (1) 0 . 5% (2) 50% (3) 2% (4) 30% JEE Main 2022 (26 Jul Shift 2) JEE Main Previous Year Paper

Q19.A hydrogen atom in its ground state absorbs 10. 2 eV of energy. The angular momentum of electron of the hydrogen atom will increase by the value of (Given, Planck's constant = 6. 6 × 10−34 Js ). (1) 2. 10 × 10−34 Js (2) 1. 05 × 10−34 Js (3) 3. 15 × 10−34 Js (4) 4. 2 × 10−34 Js