Practice Questions

Q25.A telescope of aperture 3 × 10−2 m diameter is focused on a window at 80 m distance fitted with a wire mesh of spacing 2 × 10−3 m. Given: λ = 5.5 × 10−7 m, which of the following is true for observing the mesh JEE Main 2012 (26 May Online) JEE Main Previous Year Paper through the telescope? (1) Yes, it is possible with the same aperture size. (2) Possible also with an aperture half the present diameter. (3) No, it is not possible. (4) Given data is not sufficient.

Q26.In Young's double slit interference experiment, the slit widths are in the ratio 1 : 25 . Then the ratio of intensity at the maxima and minima in the interference pattern is (1) 3 : 2 (2) 1 : 25 (3) 9 : 4 (4) 1 : 5

Q26.The electron of a hydrogen atom makes a transition from the (n + 1)th orbit to the nth orbit. For large n the wavelength of the emitted radiation is proportional to (1) n (2) n3 (3) n4 (4) n2

Q26.A hypothetical atom has only three energy levels. The ground level has energy, E1 = −8eV. The two excited states have energies, E2 = −6eV and E3 = −2eV. Then which of the following wavelengths will not be present in the emission spectrum of this atom? (1) 207 nm (2) 465 nm (3) 310 nm (4) 620 nm

Q27.In the Rutherford experiment, α-particles are scattered from a nucleus as shown. Out of the four paths, which path is not possible? (1) D (2) B (3) C (4) A

Q27.Photoelectrons are ejected from a metal when light of frequency v falls on it. Pick out the wrong statement from the following. (1) No electrons are emitted if v is less than W/h, (2) The ejection of the photoelectrons is where W is the work function of the metal instantaneous. (3) The maximum energy of the photoelectrons is hu.(4) The maximum energy of the photoelectrons is independent of the intensity of the light.

Q27.Assume that a neutron breaks into a proton and an electron. The energy released during this process is (Mass of neutron = 1.6725 × 10−27 kg; mass of proton = 1.6725 × 10−27 kg; mass of electron = 9 × 10−31 kg) (1) 0.73 MeV (2) 7.10 MeV (3) 6.30 MeV (4) 5.4 MeV

Q27.The decay constants of a radioactive substance for α and β emission are λα and λβ respectively. If the substance emits α and β simultaneously, then the average half life of the material will be (1) 2TαTβ (2) Tα + Tβ Tα+Tβ (3) TαTβ (4) 1 2 (Tα + Tβ ) Tα+Tβ

Q27.A doubly ionised Li atom is excited from its ground state(n = 1) to n = 3 state. The wavelengths of the spectral lines are given by λ32, λ31 and λ21 . The ratio λ32/λ31 and λ21/λ31 are, respectively (1) 8.1, 0.67 (2) 8.1, 1.2 (3) 6.4, 1.2 (4) 6.4, 0.67

Q28.Truth table for system of four NAND gates as shown in figure is (1) (2) (3) (4)

Q28.Which of the plots shown in the figure represents speed (v) of the electron in a hydrogen atom as a function of the principal quantum number (n) ? (1) B (2) D (3) C (4) A

Q28.Which of the following Statements is correct? (1) The rate of radioactive decay cannot be (2) Nuclear forces are short range, attractive and controlled but that of nuclear fission can be charge dependent. controlled. (3) Nuclei of atoms having same number of neutrons (4) Wavelength of matter waves is given by de are known as isobars. Broglie formula but that of photons is not given by the same formula

Q29.Which logic gate with inputs A and B performs the same operation as that performed by the following circuit? (1) NAND gate (2) OR gate (3) NOR gate (4) AND gate

Q29.Given the electric field of a complete amplitude modulated wave as Em →E = ^iEc + cos cos ωct (1 Ec ωmt) Where the subscript c stands for the carrier wave and m for the modulating signal. The frequencies present in the modulated wave are (1) ωc and √ω2c + ω2m (2) ωc, ωc + ωm and ωc −ωm (3) ωc and ωm (4) ωc and √ωcωm

Q29.The counting rate observed from a radioactive source at t = 0 was 1600 counts s−1 , and t = 8 s, it was 100 counts s−1 . The counting rate observed as counts s−1 at t = 6 s will be (1) 250 (2) 400 (3) 300 (4) 200

Q30.A spectrometer gives the following reading when used to measure the angle of a prism. Main scale reading: 58.5 degree Vernier scale reading : 09 divisions Given that 1 division on main scale corresponds to 0.5 degree. Total divisions on the vernier scale is 30 and match with 29 divisions of the main scale. The angle of the prism from the above data (1) 58.59∘ (2) 58.77∘ (3) 58.65∘ (4) 59∘

Q30.A 10 kW transmitter emits radio waves of wavelength 500 m. The number of photons emitted per second by the transmitter is of the order of (1) 1037 (2) 1031 (3) 1025 (4) 1043 JEE Main 2012 (12 May Online) JEE Main Previous Year Paper

Q31.A transition metal M forms a volatile chloride which has a vapour density of 94.8 . If it contains 74.75% of chlorine the formula of the metal chloride will be (1) MCl3 (2) MCl2 (3) MCl4 (4) MCl5

Q31.The density of a solution prepared by dissolving 120 g of urea (mol. Mass = 60u ) in 1000 g of water is 1.15 g/mL. The molarity of this solution is : (1) 0.50 M (2) 1.78 M (3) 1.02 M (4) 2.05 M JEE Main 2012 (Offline) JEE Main Previous Year Paper

Q31.An aqueous solution of oxalic acid dihydrate contains its 6.3 g in 250ml. The volume of 0.1 N NaOH required to completely neutralize 10ml of this solution (1) 4ml (2) 20ml (3) 2ml (4) 40ml Q32. 5 g of benzene on nitration gave 6.6 g of nitrobenzene. The theoretical yield of the nitrobenzene will be (1) 4.5 g (2) 5.6 g (3) 8.09 g (4) 6.6 g

Q31.The concentrated sulphuric acid that is peddled commercial is 95%H2SO4 by weight. If the density of this commercial acid is 1.834 g cm−3 , the molarity of this solution is (1) 17.8M (2) 12.0M (3) 10.5M (4) 15.7M

Q31.When CO2( g) is passed over red hot coke it partially gets reduced to CO(g). Upon passing 0.5 L of CO2(g) over red hot coke, the total volume of the gases increased to 700 mL. The composition of the gaseous mixture at STP is (1) CO2 = 300 mL; CO = 400 mL (2) CO2 = 0.0 mL; CO = 700 mL (3) CO2 = 200 mL; CO = 500 mL (4) CO2 = 350 mL; CO = 350 mL

Q32.The following sets of quantum numbers represent four electrons in an atom. (i) n = 4, l = 1 (ii) n = 4, l = 0 (iii) n = 3, l = 2 (iv) n = 3, l = 1 The sequence representing increasing order of energy, is (1) (iii) < (i) < (iv) < (ii) (2) (iv) < (ii) < (iii) < (i) (3) (i) < (iii) < (ii) < (iv) (4) (ii) < (iv) < (i) < (iii)

Q32.Which of the following paramagnetic ions would exhibit a magnetic moment (spin only) of the order of 5BM ? (At. Nos. Mn = 25, Cr = 24, V = 23, Ti = 22 ) (1) Mn2+ (2) Ti2+ (3) V2+ (4) Cr2+

Q33.Which of the following presents the correct order of second ionization enthalpies of C, N, O and F ? (1) F > O > N > C (2) O > N > F > C (3) C > N > O > F (4) O > F > N > C