Practice Questions

Q67.Wavelength of light used in an optical instrument are λ1 = 4000Å and λ2 = 5000Å, then ratio of their respective resolving powers (corresponding to λ1 and λ2 ) is (1) 16 : 25 (2) 9 : 1 (3) 4 : 5 (4) 5 : 4

Q68.Sodium and copper have work functions 2.3eV and 4.5eV respectively. Then the ratio of the wave lengths is nearest to JEE Main 2002 JEE Main Previous Year Paper (1) 1 : 2 (2) 4 : 1 (3) 2 : 1 (4) 1 : 4

Q70.If 13.6eV energy is required to ionize the hydrogen atom, then the energy required to remove an electron from n = 2 is (1) 10.2eV (2) 0eV (3) 3.4eV (4) 6.8eV

Q71.At a specific instant emission of radioactive compound is deflected in a magnetic field. The compound can emit (i) electrons (ii) protons (iii) He2+ (iv) neutrons The emission at instant can be (1) i, ii, iii (2) i, ii, iii, iv (3) iv (4) ii, iii

Q72.If N0 is the original mass of the substance of half- life period t1/2 = 5 years, then the amount of substance left after 15 years is (1) N0/8 (2) N0/16 (3) N0/2 (4) N0/4

Q73.If mass-energy equivalence is taken into account, when water is cooled to form ice, the mass of water should (1) increase (2) remain unchanged (3) decrease (4) first increase then decrease

Q74.At absolute zero, Si acts as (1) non metal (2) metal (3) insulator (4) none of these

Q75.The energy band gap is maximum in (1) metals (2) superconductors (3) insulators (4) semiconductors

Q76.The part of a transistor which is most heavily doped to produce large number of majority carriers is (1) emmiter (2) base (3) collector (4) can be any of the above three

Q79.In a hydrogen atom, if energy of an electron in ground state is 13.6 eV, then that in the 2nd excited state is JEE Main 2002 JEE Main Previous Year Paper (1) 1.51 eV (2) 3.4 eV (3) 6.04 eV (4) 13.6 eV

Q80.Uncertainity in position of a minute particle of mass 25 g in space is 10−5 m. What is the uncertainity in its velocity (in ms−1)? ( h = 6.6 × 10−34Js) (1) 2.1 × 10−34 (2) 0.5 × 10−34 (3) 2.1 × 10−28 (4) 0.5 × 10−23 Q81. β - particle is emitted in radioactivity by (1) conversion of proton to neutron (2) from outermost orbit (3) conversion of neutron to proton (4) β-particle is not emitted

Q82.In which of the folloiwng species the interatomic bond angle is 109∘28′? (1) NH3, (BF4)−1 (2) (NH4)+, BF3 (3) NH3, BF4 (4) (NH2)−1, BF3

Q88.If an endothermic reaction is non- spantaneous at freezing point of water and becomes feasible at its boiling point, then (1) ΔH is - ve, ΔS is + ve (2) ΔH and ΔS both are + ve (3) ΔH and ΔS both are − ve (4) ΔH is + ve, ΔS is −ve

Q90.The heat required to raise the temperature of body by 1 K is called JEE Main 2002 JEE Main Previous Year Paper (1) specific heat (2) thermal capacity (3) water equivalent (4) none of these

Q91.Change in volume of the system does not alter the number of moles in which of the following equilibria ? (1) N2( g) + O2( g) ⇌2NO(g) (2) PCl5( g) ⇌PCl3( g) + Cl2( g) (3) N2( g) + 3H2( g) ⇌2NH3( g) (4) SO2Cl2( g) ⇌SO2( g) + Cl2( g)