Practice Questions

Q67.Two identical photocathodes receive light of frequencies f1 and f2 . If the velocities of the photo electrons (of mass m ) coming out are respectively v1 and v2 , then (1) v21 −v22 = 2hm (f1 −f2) (2) v1 + v2 = [ 2hm (f1 + f2)] 1/2 (3) v21 + v22 = 2hm (f1 + f2) (4) v1 −v2 = [ 2hm (f1 −f2)] 1/2

Q68.Which of the following atoms has the lowest ionization potential? (1) 147 N (2) 13355 Cs (3) 4018Ar (4) 168 O

Q69.The wavelengths involved in the spectrum of deuterium (21D) are slightly different from that of hydrogen spectrum, because (1) the size of the two nuclei are different (2) the nuclear forces are different in the two cases (3) the masses of the two nuclei are different (4) the attraction between the electron and the nucleus is different in the two cases

Q70.If the binding energy of the electron in a hydrogen atom is 13.6eV, the energy required to remove the electron from the first excited state of Li++ is (1) 30.6eV (2) 13.6eV (3) 3.4eV (4) 122.4eV

Q71.Which of the following radiations has the least wavelength? (1) γ -rays (2) β-rays (3) α-rays (4) X-rays

Q72.When a U 238 nucleus originally at rest, decays by emitting an alpha particle having a speed ' u ', the recoil speed of the residual nucleus is (1) 238 4u (2) −4u234 (3) 234 4u (4) −4u238 JEE Main 2003 JEE Main Previous Year Paper

Q73.A radioactive sample at any instant has its disintegration rate 5000 disintegrations per minute. After 5 min− utes, the rate is 1250 disintegrations per minute. Then, the decay constant (per minute) is (1) 0.4 ln 2 (2) 0.2 ln 2 (3) 0.1 ln 2 (4) None of these

Q74.A nucleus with Z = 92 emits the following in a sequence: α, β−, β−α, α, α, α, α, β−, β−, α, β+, β+, α. Then Z of the resulting nucleus is (1) 76 (2) 78 (3) 82 (4) 74

Q75.Which of the following cannot be emitted by radioactive substances during their decay? (1) Protons (2) Neutrinoes (3) Helium nuclei (4) Electrons

Q76.The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the (1) crystal structure (2) variation of the number of charge carriers with temperature (3) type of bonding (4) variation of scattering mechanism with temperature

Q77.In the middle of the depletion layer of a reverse biased p-n junction, the (1) electric field is zero (2) potential is maximum (3) electric field is maximum (4) potential is zero

Q78.Consider telecommunication through optical fibres. Which of the following statements is not true? (1) Optical fibres can be of graded refractive index (2) Optical fibres are subjective to electromagnetic interference from outside (3) Optical fibres have extremely low transmission (4) Optical fibres may have homogeneous core with loss a suitable cladding.

Q79.What volume of hydrogen gas, at 273 K and 1 atm, pressure will be consumed in obtaining 21.6 g of elemental boron (atomic mass = 10.8 ) from the reducti on of boron trichloride by hydrogen? (1) 67.2 L (2) 44.8 L (3) 22.4 L (4) 89.6 L Q80. 25ml of a solution of barrium hydroxide on titration with a 0.1 molar solution of hydrochloric acid gave a litre value of 35ml. The molarity of barium hydroxide solution was (1) 0.14 (2) 0.28 (3) 0.35 (4) 0.07

Q81.The orbital angular momentum for an electron revolving in an orbit is given by √l(l + 1) ⋅ 2πh . This momentum for an s-electron will be given by (1) zero (2) h 2π (3) √2 ⋅ 2πh (4) + 21 ⋅ 2πh JEE Main 2003 JEE Main Previous Year Paper

Q82.Which one of the following groupings represents a collection of isoelectronic species? (At. nos,: 55, Br:35) (1) N3−, F−, Na+ (2) Be, Al3+, Cl− (3) Ca2+, Cs+, Br (4) Na+, Ca2+, Mg2+

Q83.In Bohr series of lines of hydrogen spectrum, the third line from the red end corresponds to which one of the following inter-orbit jumps of the electron for Bohr orbits in an atom of hydrogen (1) 5 →2 (2) 4 →1 (3) 2 →5 (4) 3 →2

Q84.The de Broglie wavelength of a tennis ball of mass 60 g moving with a velocity of 10 metres per second is approximately (1) 10−31 metres (2) 10−16 metres (3) 10−25 metres (4) 10−33 metres Planck's constant, h = 6.63 × 10−34Js.

Q85.The radionucleide 23490 Th undergoes two successive β-decays followed by one α-decay. The atomic number and the mass number respectively of the resulting radionucleide are (1) 94 and 230 (2) 90 and 230 (3) 92 and 230 (4) 92 and 234

Q86.According to the Periodic Law of elements, the variation in properties of elements is related to their (1) nuclear masses (2) atomic numbers (3) nuclear neutron-proton number ratios (4) atomic masses

Q87.Which one of the following substances has the highest proton affinity? (1) H2 S (2) NH3 (3) PH3 (4) H2O

Q88.Which one of the following pairs of molecules will have permanent dipole moments for both members? (1) NO2 and CO2 (2) NO2 and O3 (3) SiF4 and CO2 (4) SiF4 and NO2

Q89.Which one of the following compounds has the smallest bond angle in its molecule? (1) OH2 (2) SH2 (3) NH3 (4) SO2

Q90.The pair of species having identical shapes for molecules of both species is (1) XeF2, CO2 (2) BF3, PCl3 (3) PF5, IF5 (4) CF4, SF4

Q91.According to the kinetic theory of gases, in an ideal gas, between two successive collisions a gas molecule travels (1) in a wavy path (2) in a straight line path (3) with an accelerated velocity (4) in a circular path JEE Main 2003 JEE Main Previous Year Paper

Q92.The internal energy change when a system goes from state A to B is 40 kJ/mole. If the system goes from A to B by a reversible path and retums to state A by an irreversible path what would be the net change in internalenergy? (1) > 40 kJ (2) < 40 kJ (3) Zero (4) 40 kJ