Practice Questions

Q18.A radioactive material decays by simultaneous emissions of two particles with half lives of 1400 years and 700 years, respectively. What will be the time after the which one third of the material remains ? (Take ln 3 = 1. 1 ) (1) 1110 years (2) 700 years (3) 340 years (4) 740 years

Q18.In a photoelectric experiment, increasing the intensity of incident light: (1) increases the number of photons incident and also (2) increases the frequency of photons incident and increases the K.E. of the ejected electrons. increases the K.E. of the ejected electrons. (3) increases the number of photons incident and the (4) increases the frequency of photons incident and K.E. of the ejected electrons remains unchanged. the K.E. of the ejected electrons remains unchanged.

Q18.In Young's double slit experiment, if the source of light changes from orange to blue then: (1) the central bright fringe will become a dark (2) the distance between consecutive fringes will fringe. decrease. (3) the distance between consecutive fringes will (4) the intensity of the minima will increase. increase.

Q18.The speed of electrons in a scanning electron microscope is 1 × 107 ms−1 . If the protons having the same speed are used instead of electrons, then the resolving power of scanning proton microscope will be changed by a factor of: (1) 1837 (2) 18371 (3) √1837 (4) 1 √1837

Q18.An electron and proton are separated by a large distance. The electron starts approaching the proton with energy 3 eV . The proton captures the electrons and forms a hydrogen atom in second excited state. The resulting photon is incident on a photosensitive metal of threshold wavelength 4000A What is the maximum kinetic energy of the emitted photoelectron? JEE Main 2021 (27 Jul Shift 2) JEE Main Previous Year Paper (1) 7. 61 eV (2) 1. 41 eV (3) 3. 3 eV (4) No photoelectron would be emitted

Q18.The recoil speed of a hydrogen atom after it emits a photon in going from n = 5 state to n = 5 state will be (1) 4. 17 m s−1 (2) 2. 19 m s−1 (3) 4. 34 m s−1 (4) 3. 25 m s−1

Q18.The atomic hydrogen emits a line spectrum consisting of various series. Which series of hydrogen atomic spectra is lying in the visible region? (1) Brackett series (2) Paschen series (3) Lyman series (4) Balmer series

Q19.If 𝑉𝐴 and 𝑉𝐵 are the input voltages (either 5 V or 0 V) and V0 is the output voltage then the two gates represented in the following circuits 𝐴 and 𝐵 are : (1) OR and NOT Gate (2) AND and NOT Gate (3) AND and OR Gate (4) NAND and NOR Gate

Q19.Given below are two statements: Statement I : A speech signal of 2 kHz is used to modulate a carrier signal of 1 MHz. The bandwidth requirement for the signal is 4 kHz. Statement II : The side band frequencies are 1002 kHz and 998 kHz. In the light of the above statements, choose the correct answer from the options given below: (1) Statement I is false but Statement II is true (2) Both Statement I and Statement II are true (3) Statement I is true but Statement II is false (4) Both Statement I and Statement II are false

Q19.Statement I: By doping silicon semiconductors with pentavalent material, the electrons density increases. Statement II: The n−type of semiconductor has a net negative charge. In the above statements, choose the most appropriate answer from the options given below: (1) Both Statement I and Statement II are false. (2) Statement I is true but Statement II is false. (3) Statement I is false but Statement II is true. (4) Both Statement I and Statement II are true.

Q19.An electron having de-Broglie wavelength λ is incident on a target in a X -ray tube. Cut-off wavelength of emitted X -ray is: (1) 0 (2) 2 m2c2λ2 h2 (3) 2mcλ2 (4) hc h mc

Q19.Identify the logic operation carried out. (1) OR (2) AND (3) NOR (4) NAND

Q19.Choose the correct waveform that can represent the voltage across R of the following circuit, assuming the diode is ideal one: JEE Main 2021 (31 Aug Shift 1) JEE Main Previous Year Paper (1) (2) (3) (4)

Q19.For extrinsic semiconductors; when doping level is increased; (1) Fermi-level of p and n- type semiconductors will not be affected. (2) Fermi-level of p-type semiconductor will go upward and Fermi-level of n-type semiconductors will go downward. (3) Fermi-level of both p-type and n-type semiconductors will go upward for T > TF K and downward for T < TF K, where TF is Fermi temperature. (4) Fermi-level of p- type semiconductors will go downward and Fermi-level of n- type semiconductor will go upward.

Q19.Consider a situation in which reverse biased current of a particular P −N junction increases when it is exposed to a light of wavelength ≤621 nm. During this process, enhancement in carrier concentration takes place due to generation of hole-electron pairs. The value of band gap is nearly. (1) 2 eV (2) 4 eV (3) 1 eV (4) 0. 5 eV

Q19.Zener breakdown occurs in a p −n junction having pand n both: (1) lightly doped and have narrow depletion layer. (2) heavily doped and have wide depletion layer. (3) lightly doped and have wide depletion layer. (4) heavily doped and have narrow depletion layer.

Q19.Which one of the following will be the output of the given circuit? (1) NOR Gate (2) NAND Gate (3) AND Gate (4) XOR Gate

Q19.For a transistor α and β are given as α = IC and β = IC . Then the correct relation between α and β will be: IE IB (1) α = 1−ββ (2) αβ = 1 (3) β = 1−αα (4) α = 1−ββ

Q19.The half life period of a radioactive element 𝑥 is same as the mean life time of another radioactive element 𝑦. Initially they have the same number of atoms. Then: (1) 𝑥 and 𝑦 decay at the same rate always. (2) 𝑥-will decay faster than 𝑦. (3) 𝑦-will decay faster than 𝑥. (4) 𝑥 and 𝑦 have same decay rate initially and later on different decay rate. JEE Main 2021 (01 Sep Shift 2) JEE Main Previous Year Paper

Q19.The stopping potential in the context of photoelectric effect depends on the following property of incident electromagnetic radiation: (1) Phase (2) Intensity (3) Amplitude (4) Frequency

Q19.Four NOR gates are connected as shown in figure. The truth table for the given figure is : (1) A B Y (2) A B Y 0 0 1 0 0 0 0 1 0 0 1 1 1 0 1 1 0 1 1 1 0 1 1 0 (3) A B Y (4) A B Y 0 0 1 0 0 0 0 1 0 0 1 1 1 0 0 1 0 0 1 1 1 1 1 1

Q19.A radioactive sample disintegrates via two independent decay processes having half lives T (1) and T (2) 1/2 1/2 respectively. The effective half- life T1/2 of the nuclei is : (1) (2) T 1/2+T 1/2 (1) T (2) (2) T1/2 = T 1/2(1) + 1/2 T1/2 = (1) (2) T 1/2−T 1/2 (3) T 1/2T(1) 1/2(2) (4) None of the above T1/2 = (1) (2) T 1/2+T 1/2

Q19.A nucleus of mass M emits γ -ray photon of frequency v. The loss of internal energy by the nucleus is: [Take c as the speed of electromagnetic wave] (1) hv (2) 0 (3) hv[1 − 2Mc2hv ] (4) hv[1 + 2Mc2hv ]

Q19.If λ1 and λ2 are the wavelengths of the third member of Lyman and first member of the Paschen series respectively, then the value of λ1 : λ2 is : (1) 7 : 135 (2) 1 : 9 (3) 1 : 3 (4) 7 : 108

Q19.The output of the given combination gates represents: JEE Main 2021 (17 Mar Shift 1) JEE Main Previous Year Paper (1) XOR Gate (2) NAND Gate (3) AND Gate (4) NOR Gate