Practice Questions

Q25.If the maximum value of accelerating potential provided by a radio frequency oscillator is 12 kV . The number of revolution made by a proton in a cyclotron to achieve one sixth of the speed of light is: [mp = 1. 67 × 10−27 kg, e = 1. 6 × 10−19 C, Speed of light = 3 × 108 m s−1]

Q25.A particle of mass 1 mg and charge 𝑞 is lying at the mid-point of two stationary particles kept at a distance 2 m when each is carrying same charge 𝑞. If the free charged particle is displaced from its equilibrium position through distance 𝑥 𝑥< < 1 m. The particle executes SHM. Its angular frequency of oscillation will be _______ × 105 rad s-1 (if 𝑞2 = 10𝐶2)

Q26.A light beam of wavelength 500 nm is incident on a metal having work function of 1. 25 eV , placed in a magnetic field of intensity B. The electrons emitted perpendicular to the magnetic field B, with maximum kinetic energy are bent into a circular arc of radius 30 cm. The value of B is ________ ×10−7 T. Given hc = 20 × 10−26 J m, the mass of the electron = 9 × 10−31 kg. JEE Main 2021 (25 Jul Shift 2) JEE Main Previous Year Paper

Q27.A closed organ pipe of length L and an open organ pipe contain gases of densities ρ1 and ρ2 respectively. The compressibility of gases are equal in both the pipes. Both the pipes are vibrating in their first overtone with same frequency. The length of the open pipe is x , where x is _______. 3 L√ρ1ρ2 (Round off to the Nearest Integer)

Q27.Two short magnetic dipoles m1 and m2 each having magnetic moment of 1 A m2 are placed at point O and P respectively. The distance between OP is 1 m . The torque experienced by the magnetic dipole m2 due to the presence of m1 is ________ × 10−7N m

Q28.A radioactive sample has an average life of 30 ms and is decaying. A capacitor of capacitance 200 μF is first charged and later connected with resistor R. If the ratio of the charge on the capacitor to the activity of the radioactive sample is fixed with respect to time then the value of R should be _______Ω.

Q28.A circular conducting coil of radius 1 m is being heated by the change of magnetic field →𝐵 passing perpendicular to the plane in which the coil is laid. The resistance of the coil is 2 μΩ. The magnetic field is slowly switched off such that its magnitude changes in time as 4 𝑡 𝐵= 𝜋× 10-3 𝑇1 - 100 The energy dissipated by the coil before the magnetic field is switched off completely is 𝐸= ______mJ.

Q28.Seawater at a frequency f = 9 × 102 Hz , has permittivity ε = 80ε0 and resistivity ρ = 0. 25 Ω m . Imagine a parallel plate capacitor is immersed in seawater and is driven by an alternating voltage source V (t) = V0 sin(2πft). Then the conduction current density becomes 10x times the displacement current density after time t = 8001 s. The value of x is _______ (Given : 1 = 9 × 109 N m2 4πε0 C−2)

Q28.An object is placed at a distance of 12 cm from a convex lens. A convex mirror of focal length 15 cm is placed on another side of the lens at 8 cm as shown in the figure. The image of the object coincides with the object. When the convex mirror is removed, a real and inverted image is formed at a position. The distance of the image from the object will be ___ cm JEE Main 2021 (26 Aug Shift 2) JEE Main Previous Year Paper

Q28.Two stream of photons, possessing energies equal to twice and ten times the work function of metal are incident on the metal surface successively. The value of ratio of maximum velocities of the photoelectrons emitted in the two respective cases is x : 3 The value of x is

Q29.Two satellites revolve around a planet in coplanar circular orbits in anticlockwise direction. Their period of revolutions are 1 hour and 8 hours respectively. The radius of the orbit of nearer satellite is 2 × 103 km . The angular speed of the farther satellite as observed from the nearer satellite at the instant when both the satellites are closest is 𝜋 h-1, where 𝑥 is _______ . 𝑥rad

Q29.The Kα X-ray of molybdenum has wavelength 0. 071 nm. If the energy of a molybdenum atom with a K electron knocked out is 27. 5 keV, the energy of this atom when an L electron is knocked out will be keV. (Round off to the nearest integer ) [h = 4. 14 × 10−15 eV s, c = 3 × 108 m s−1]

Q29.An object viewed from a near point distance of 25 cm, using a microscopic lens with magnification 6, gives an unresolved image. A resolved image is observed at infinite distance with a total magnification double the earlier using an eyepiece along with the given lens and a tube of length 0. 6 m, if the focal length of the eyepiece is equal to ____ cm.

Q30.A deviation of 2° is produced in the yellow ray when prism of crown and flint glass are achromatically combined. Taking dispersive powers of crown and flint glass are 0. 02 and 0. 03 respectively and refractive JEE Main 2021 (16 Mar Shift 2) JEE Main Previous Year Paper index for yellow light for these glasses are 1. 5 and 1. 6 respectively. The refracting angles for crown glass prism will be ________ ° (in degree) (Round off to the Nearest Integer)

Q30.A particle of mass m moves in a circular orbit in a central potential field U(r) = U0r4. If Bohr's quantization α , where α is _______ . conditions are applied, radii of possible orbitals rn vary with n 1

Q31.Complete combustion of 1. 80 g of an oxygen containing compound (CxHyOz) gave 2. 64 g of CO2 and 1. 08 g of H2O. The percentage of oxygen in the organic compound is : (1) 53. 33 (2) 50. 33 (3) 51. 63 (4) 63. 53

Q35.Which of the following equation depicts the oxidizing nature of H2O2 ? (1) 2I−+ H2O2 + 2H+ →I2 + 2H2O (2) I2 + H2O2 + 2 OH−→2I−+ 2H2O + O2 (3) Cl2 + H2O2 →2HCl + O2 (4) KIO4 + H2O2 →KIO3 + H2O + O2

Q36. Correct statement about the given chemical reaction is (1) Reaction is possible and compound (A) will be (2) −¨NH2 group is ortho and para directive, so major product. product (B) is not possible. (3) Reaction is possible and compound (B) will be (4) The reaction will form sulphonated product the major product. instead of nitration.

Q37.What is the correct sequence of reagents used for converting nitrobenzene into m -dibromobenzene? (1) Sn / HCl KBr Br2 H+ (2) Br2 / Fe Sn / HCl NaNO2 / HCl CuBr / HBr−−−−−−→ / → / →/ → → / → / → / → (3) NaNO2 HCl KBr H+ (4) Sn / HCl Br2 NaNO2 NaBr−−−−−−→ / → / → / → → / →/ → / →

Q38.The correct sequence of correct reagents for the following transformation is :- (1) (i) Fe, HCl (2) (i) Fe, HCl (ii) Cl2, HCl, (ii) NaNO2, HCl, 0°C (iii) NaNO2, HCl, 0°C (iii) H2O/H+ (iv) H2O/H+ (iv) Cl2, FeCl3 (3) (i) Cl2, FeCl3 (4) (i) Cl2, FeCl3 (ii) Fe, HCl (ii) NaNO2, HCl, 0°C (iii) NaNO2, HCl, 0°C (iii) Fe, HCl (iv) H2O/H+ (iv) H2O/H+

Q38. Consider the given reaction, percentage yield of : (1) C > A > B (2) B > C > A (3) A > C > B (4) C > B > A

Q38.The correct sequence of reagents used in the preparation of 4 -bromo- 2-nitroethylbenzene from benzene is : JEE Main 2021 (25 Feb Shift 2) JEE Main Previous Year Paper (1) CH3 COCl / AlCl3, Br2 / AlBr3, HNO3 /H2 SO4, Zn / HCl (2) CH3 COCl / AlCl3, Zn −Hg / HCl, Br2 / AlBr3, HNO3 /H2 SO4 (3) HNO3 /H2 SO4, Br2 / AlCl3, CH3 COCl / AlCl3, Zn −Hg / HCl (4) Br2 / AlBr3, CH3 COCl / AlCl3, HNO3 /H2 SO4, Zn / HCl

Q44.The correct order of intensity of colors of the compounds is: (1) [Ni(CN)4]2−> [NiCl4]2−> [Ni (H2O)6]2+ (2) [Ni (H2O)6]2+ > [NiCl4]2−> [Ni(CN)4]2− (3) [NiCl4]2−> [Ni (H2O)6]2+ > [Ni(CN)4]2− (4) [NiCl4]2−> [Ni(CN)4]2−> [Ni (H2O)6]2+ C2H5 OH −

Q44.The Crystal Field Stabilization Energy (CFSE) and magnetic moment (spin-only) of an octahedral aqua complex of a metal ion M𝑍+ are -0 . 8Δ0 and 3 . 87 BM, respectively. Identify M𝑍+ : (1) V3 + (2) Co2 + (3) Cr3 + (4) Mn4 +

Q45.Which one of the following complexes is violet in colour? (1) Fe4 [Fe(CN)6]3 ⋅H2O (2) [Fe(CN)5 NOS]4− (3) [Fe(SCN)6]4− (4) [Fe(CN)6]4−