Practice Questions

Q17.Two radioactive substances X and Y originally have N1 and N2 nuclei respectively. Half life of X is half of the half life of Y . After three half lives of Y , number of nuclei of both are equal. The ratio N1 will be equal to N2 : (1) 1 (2) 8 3 1 (3) 3 (4) 1 1 8

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 an electromagnetic wave, the electric field vector and magnetic field vector are given as E = E0ˆi and → B = B0ˆk, respectively. The direction of propagation of electromagnetic wave is along: (1) (ˆk) (2) ˆJ (3) (−ˆk) (4) (−ˆj)

Q18.A nucleus with mass number 184 initially at rest emits an α− particle. If the Q value of the reaction is 5. 5 MeV, calculate the kinetic energy of the α− particle. (1) 5. 0 MeV (2) 5. 5 MeV (3) 0. 12 MeV (4) 5. 38 MeV

Q18.In a Young's double slit experiment two slits are separated by 2 mm and the screen is placed one meter away. When a light of wavelength 500 nm is used, the fringe separation will be : (1) 1 mm (2) 0. 50 mm (3) 0. 75 mm (4) 0. 25 mm

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.A ray of light entering from air into a denser medium of refractive index 4 , as shown in figure. 3 The light ray suffers total internal reflection at the adjacent surface as shown. The maximum value of angle θ should be equal to: JEE Main 2021 (25 Jul Shift 2) JEE Main Previous Year Paper (1) sin−1 √73 (2) sin−1 √54 (3) sin−1 √74 (4) sin−1 √53

Q18.Which level of the single ionized carbon has the same energy as the ground state energy of hydrogen atom? (1) 1 (2) 6 (3) 4 (4) 8

Q18.A 5 V battery is connected across the points X and Y . Assume D1 and D2 to be normal silicon diodes. Find the current supplied by the battery if the +ve terminal of the battery is connected to point X . (1) ~0. 86 A (2) ~0. 5 A (3) ~1. 5 A (4) ~0. 43 A

Q18.A monochromatic neon lamp with wavelength of 670. 5 nm illuminates a photo-sensitive material which has a stopping voltage of 0. 48 V . What will be the stopping voltage if the source light is changed with another source of wavelength of 474. 6 nm ? (1) 0. 24 V (2) 1. 5 V (3) 1. 25 V (4) 0. 96 V

Q18.Identify the logic operation carried out by the given circuit: (1) OR (2) AND (3) NAND (4) NOR

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.Given below are two statements: Statement I: Two photons having equal linear momenta have equal wavelengths. Statement II: If the wavelength of the photon is decreased, then the momentum and energy of a photon will also decrease. In the light of the above statements, choose the correct answer from the options given below. (1) Both Statement I and Statement II are false (2) Both Statement I and Statement II are true (3) Statement I is true but Statement II is false (4) Statement I is false but Statement II is true

Q18.The temperature of an ideal gas in three dimensions is 300 K . The corresponding de-Broglie wavelength of the electron approximately at 300 K is: 𝑚𝑒= mass of electron = 9 × 10-31 kg, ℎ= Planck constant = 6 . 6 × 10-34 J s, 𝑘𝐵= Boltzmann constant = 1 . 38 × 10-23 J K-1 (1) 2 . 26 nm (2) 3 . 25 nm (3) 8 . 46 nm (4) 6 . 26 nm

Q18.Imagine that the electron in a hydrogen atom is replaced by a muon (μ). The mass of muon particle is 207 times that of an electron and charge is equal to the charge of an electron. The ionization potential of this hydrogen atom will be:- (1) 13. 6 eV (2) 2815. 2 eV (3) 331. 2 eV (4) 27. 2 eV JEE Main 2021 (18 Mar Shift 1) JEE Main Previous Year Paper

Q18.A free electron of 2 . 6 eV energy collides with a H+ ion. This results in the formation of a hydrogen atom in the first excited state and a photon is released. Find the frequency of the emitted photon. ℎ= 6 . 6 × 10-34 J s (1) 9 . 0 × 1027 MHz (2) 1 . 45 × 109 MHz (3) 0 . 19 × 1015 MHz (4) 1 . 45 × 1016 MHz

Q18.The truth table for the following logic circuit is : (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.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.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 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.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.An electron moving with speed v and a photon moving with speed c, have the same D-Broglie wavelength. The ratio of the kinetic energy of the electron to that of a photon is: (1) 3c (2) v v 3c (3) v (4) 2c 2c v

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.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