Practice Questions

Q24.A ray of light is incident at an angle of 60∘ on one face of a prism of angle 30∘ . The emergent ray of light makes an angle of 30∘ with incident ray. The angle made by the emergent ray with second face of prism will be: (1) 0° (2) 90° (3) 30° (4) 45°

Q25.Unpolarized light of intensity I is incident on a system of two polarizers, A followed by B. The intensity of emergent light is I . If a third the polarizer C is placed between A and B the intensity of emergent light is 2 reduced to I . The angle between the polarizers A and C is θ , then 3 (1) 2 41 (2) 1 41 cos θ = ( 3 ) cos θ = ( 3 ) (3) 1 21 (4) 2 21 cos θ = ( 3 ) cos θ = ( 3 )

Q25.Two electrons are moving with non-relativistic speeds perpendicular to each other. If corresponding de brogile wavelengths are λ1 and λ2 , their de brogile wavelength in the frame of reference attached to their centre of mass is: 2λ1λ2 (1) 1 = 1 + 1 (2) λCM = λCM λ1 λ2 √λ12+λ22 (3) λCM = λ1 = λ2 (4) λCM = λ1+λ22

Q25.Unpolarized light of intensity I passes through an ideal polariser A . Another identical polariser B is placed behind A . The intensity of light beyond B is found to be I . Now another identical polariser C is placed 2 between A and B. The intensity beyond B is now found to be I . The angle between polariser A and C is 8 (1) 60° (2) 0° (3) 30° (4) 45°

Q25.A plane polarized light is incident on a polariser with its pass axis making angle θ with x -axis, as shown in the figure. At four different values of θ, θ = 8∘, 38∘, 188∘ and 218∘ , the observed intensities are same. What is the angle between the direction of polarization and x -axis (1) 203∘ (2) 45∘ (3) 98∘ (4) 128∘

Q25.Two electrons are moving with non-relativistic speeds perpendicular to each other. If corresponding de Broglie wavelengths are λ1 and λ2 , their de Broglie wavelength in the frame of reference attached to their centre of mass is: (1) λCM = λ1 = λ2 (2) 1 = 1 + 1 λ1 λ1 λ2 2λ1λ2 λ1+λ2 (3) λCM = (4) λCM = 2 ( ) 1+λ22 √λ2

Q26.If the de Broglie wavelengths associated with a proton and an α-particle are equal, then the ratio of velocities of the proton and the α-particle will be: (1) 1 : 4 (2) 1 : 2 (3) 4 : 1 (4) 2 : 1

Q26.The de-Broglie wavelength (λB) associated with the electron orbiting in the second excited state of hydrogen atom is related to that in the ground state (λG) by: (1) λB = 3λG (2) λB = 2λG (3) λB = λ G (4) λB = λ G 3 2

Q26.The energy required to remove the electron from a singly ionized Helium atom is 2.2 times the energy required to remove an electron from Helium atom. The total energy required to ionize the Helium atom completely is: (1) 20eV (2) 79eV (3) 109eV (4) 34eV JEE Main 2018 (15 Apr Shift 1 Online) JEE Main Previous Year Paper

Q26.The energy required to remove the electron from a singly ionized Helium atom is 2. 2 times the energy required to remove an electron from helium atom. The total energy required to ionize the Helium atom completely is close to JEE Main 2018 (15 Apr) JEE Main Previous Year Paper (1) 34 eV (2) 20 eV (3) 79 eV (4) 109 eV

Q27.An electron from various excited states of hydrogen atom emit radiation to come to the ground state. Let λn, λg be the de Broglie wavelength of the electron in the nth state and the ground state respectively. Let ∧n be the wavelength of the emitted photon in the transition from the nth state to the ground state. For large n, (A, B are constants) (1) ∧2n ≈λ (2) ∧n ≈A + λ2nB (3) ∧n ≈A + Bλn (4) ∧2n ≈A + Bλ2n

Q27.Muon (μ−1) is negatively charged (|q| = |e|) with a mass mμ = 200 me , where me is the mass of the electron and e is the electronic charge. If μ−1 is bound to a proton to form a hydrogen like atom, identify the correct statements (A) Radius of the muonic orbit is 200 times smaller than that of the electron (B) the speed of the μ−1 in the nth orbit is 1 times that of the election in the nth orbit (C) The lonization energy of muonic atom 200 is 200 times more than that of an hydrogen atom (D) The momentum of the muon in the nth orbit is 200 times more than that of the electron (1) (A), (B), (D) (2) (B), (D) (3) (C),(D) (4) (A), (C), (D)

Q27.A solution containing active cobalt 6027Co having activity of 0.8μCi and decay constant λ is injected in an animal's body. If 1 cm3 of blood is drawn from the animal's body after 10hrs of injection, the activity found was 300 decays per minute. What is the volume of blood that is flowing in the body? (1Ci = 3.7 × 1010 decay per second and at t = 10hrs−λt = 0.84) (1) 6 litres (2) 7 litres (3) 4 litres (4) 5 litres

Q27.Both the nucleus and the atom of some element are in their respective first excited states. They get de-excited by emitting photons of wavelengths λN, λA respectively. The ratio λN is closest to: λA (1) 10−1 (2) 10−6 (3) 10 (4) 10−10 JEE Main 2018 (16 Apr Online) JEE Main Previous Year Paper

Q27.A solution containing active cobalt 6027Co having an activity of 0 .8 μCi and decay constant λ is injected in an animal's body. When 1 cm3 blood is drawn from the animal's body after 10 h of injection, the activity was found to be 300 dpm(decays per minute), then the total volume of blood in the animal's body is close to [1 Ci = 3 .7 ×1010 dps(decays per second) and at t = 10 h the value of e−λt = 0.84] (1) 4 L (2) 6 L (3) 5 L (4) 7 L

Q28.In a common emitter configuration with suitable bias, it is given than RL is the load resistance and RBE is small signal dynamic resistance (input side). Then, voltage gain, current gain and power gain are given, respectively, by: [ β is current gain, IB, IC, IE are respectively base, collector and emitter currents] (1) β RL , ΔIE , β2 RL (2) β2 RL , ΔIC , β RL RBE ΔIB RBE RBE ΔIB RBE (3) β2 RL , ΔIC , β2 RL (4) β RL , ΔIC , β2 RL RBE ΔIE RBE RBE ΔIB RBE

Q28.An unstable heavy nucleus at rest breaks into two nuclei which move away with velocities in the ratio of 8 : 27 . The ratio of the radii of the nuclei (assumed to be spherical ) is: (1) 8 : 27 (2) 2 : 3 (3) 3 : 2 (4) 4 : 9 JEE Main 2018 (15 Apr Shift 2 Online) JEE Main Previous Year Paper

Q28.In a common emitter configuration with suitable bias, it is given that RL is the load resistance and RBE is small-signal dynamic resistance (input side). Then, voltage gain, current gain and power gain are given, respectively, by: β is current gain, IB , IC and IE are respectively base, collector, and emitter currents. (1) β RL , ΔIC , β2 RL (2) β RL , ΔIE , β2 RL RBE ΔIB RBE RBE ΔIB RBE (3) β2 RL , ΔIC , β RL (4) β2 RL , ΔIC , β2 RL RBE ΔIB RBE RBE ΔIE RBE

Q28.If the series limit frequency of the Lyman series is VL, then the series limit frequency of the Pfund series is: (1) VL25 (2) 25 VL (3) 16 VL (4) VL16

Q28.At some instant, a radioactive sample S1 having an activity 5μCi has twice the number of nuclei as another sample S2 which has an activity of 10μCi. The half lives of S1 and S2 are : (1) 4 : 1 (2) 1 : 4 (3) 1 : 2 (4) 2 : 1

Q29. Truth table for the given circuit will be (1) (2) x y z x y z 0 0 1 0 0 0 0 1 1 0 1 0 1 0 1 1 0 0 1 1 0 1 1 1 (3) (4) x y z x y z 0 0 1 0 0 0 0 1 1 0 1 1 1 0 1 1 0 1 1 1 1 1 1 1

Q29.The reading of the ammeter for a silicon diode in the given circuit is: (1) 13 .5 mA (2) 0 (3) 15 mA (4) 11 .5 mA

Q29.The number of amplitude-modulated broadcast stations that can be accommodated in a 300 kHz bandwidth for the highest modulating frequency 15 kHz will be: (1) 15 (2) 20 (3) 8 (4) 10

Q29.The number of amplitude modulated broadcast stations that can be accommodated in a 300kHz band width for the highest modulating frequency 15kHz will be: (1) 20 (2) 10 (3) 8 (4) 15

Q29.In the given circuit the current through zener diode is: (1) 3. 3 mA (2) 2. 5 mA (3) 5. 5 mA (4) 6. 7 mA