Practice Questions

Q26.In an experiment on photoelectric effect, a student plots stopping potential V0 against reciprocal of the wavelength λ of the incident light for two different metals A and B. These are shown in the figure. JEE Main 2013 (25 Apr Online) JEE Main Previous Year Paper Looking at the graphs, you can most appropriately say that: (1) Work function of metal B is greater than that of (2) For light of certain wavelength falling on both metal A metal, maximum kinetic energy of electrons emitted from A will be greater than those emitted from B. (3) Work function of metal A is greater than that of (4) Students data is not correct metal B

Q27.A copper ball of radius 1 cm and work function 4.47 eV is irradiated with ultraviolet radiation of wavelength 2500 Å . The effect of irradiation results in the emission of electrons from the ball. Further the ball will acquire charge and due to this there will be a finite value of the potential on the ball. The charge acquired by the ball is : (1) 5.5 × 10−13 C (2) 7.5 × 10−13 C (3) 4.5 × 10−12 C (4) 2.5 × 10−11 C

Q27.In the Bohr model an electron moves in a circular orbit around the proton. Considering the orbiting electron to be a circular current loop, the magnetic moment of the hydrogen atom, when the electron is in nth excited state, is : m e ) nh2π (1) ( 2me n2h2π ) (2) ( (3) ( 2me ) nh2π (4) ( me ) n2h2π JEE Main 2013 (09 Apr Online) JEE Main Previous Year Paper

Q27.In the Bohr's model of hydrogen-like atom the force between the nucleus and the electron is modified as e2 1 F = + β , where β is a constant. For this atom, the radius of the nth orbit in terms of the Bohr 4πε0 ( r2 r3 ) ε0h2 radius = is : (a0 mπe2 ) (1) rn = a0n −β (2) rn = a0n2 + β (3) rn = a0n2 −β (4) rn = a0n + β JEE Main 2013 (23 Apr Online) JEE Main Previous Year Paper

Q27.The anode voltage of a photocell is kept fixed. The wavelength λ of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as follows : (1) (2) (3) (4)

Q27.This question has Statement-1 and Statement-2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement-1: In Young's double slit experiment, the number of fringes observed in the field of view is small with longer wavelength of light and is large with shorter wavelength of light. Statement-2: In the double slit experiment the fringe width depends directly on the wavelength of light. (1) Statement-1 is true, Statement-2 is true and the (2) Statement-1 is false and the Statement-2 is true. Statement-2 is correct explanation of the Statement-1. (3) Statement-1 is true Statement-2 is true and the (4) Statement-1 is true and the Statement-2 is false. Statement-2 is not correct explanation of the Statement-1.

Q28.When Uranium is bombarded with neutrons, it undergoes fission. The fission reaction can be written as : 92U235 + 0n1 →56Ba141 + 36Kr92 + 3x + Q( energy) where three particles named x are produced and energy Q is released. What is the name of the particle x ? (1) electron (2) α-particle (3) neutron (4) neutrino

Q28.In a hydrogen like atom electron makes transition from an energy level with quantum number n to another with quantum number (n −1). If n >> 1, the frequency of radiation emitted is proportional to : (1) 1 (2) 1 n3/2 n3 (3) 1 (4) 1 n n2

Q28.Orbits of a particle moving in a circle are such that the perimeter of the orbit equals an integer number of de- Broglie wavelengths of the particle. For a charged particle moving in a plane perpendicular to a magnetic field, the radius of the nth orbital will therefore be proportional to : JEE Main 2013 (22 Apr Online) JEE Main Previous Year Paper (1) n2 (2) n (3) n1/2 (4) n1/4

Q28.A system of four gates is set up as shown. The 'truth table' corresponding to this system is : (1) (2) (3) (4)

Q28.A 12.5eV electron beam is used to bombard gaseous hydrogen at room temperature. It will emit: (1) 2 lines in the Lyman series and 1 line in the (2) 3 lines in the Lyman series Balmar series (3) 1 line in the Lyman series and 2 lines in the (4) 3 lines in the Balmer series Balmar series

Q29. Which of the following circuits correctly represents the following truth table ? (1) (2) (3) (4) JEE Main 2013 (25 Apr Online) JEE Main Previous Year Paper

Q29.The half-life of a radioactive element A is the same as the mean-life of another radioactive element B. Initially both substances have the same number of atoms, then : (1) A and B decay at the same rate always. (2) A and B decay at the same rate initially. (3) A will decay at a faster rate than B. (4) B will decay at a faster rate than A .

Q29.Consider two npn transistors as shown in figure. If 0 Volts corresponds to false and 5 Volts correspond to true then the output at C corresponds to : (1) A NAND B (2) A OR B (3) AAND B (4) ANOR B

Q29.A diode detector is used to detect an amplitude modulated wave of 60% modulation by using a condenser of capacity 250 pico farad in parallel with a load resistance of 100 kilo ohm. Find the maximum modulated frequency which could be detected by it. (1) 5.31 MHz (2) 5.31 kHz (3) 10.62 MHz (4) 10.62 kHz

Q29.Which of the following statement is NOT correct? (1) Ground wave signals are more stable than the sky (2) The critical frequency of an ionospheric layer is wave signals. the highest frequency that will be reflected back by the layer when it is vertically incident. (3) Electromagnetic waves of frequencies higher (4) Sky wave signals in the broadcast frequency than about 30MHz cannot penetrate the range are stronger at night than in the day time. ionosphere.

Q30.Figure shows a circuit in which three identical diodes are used. Each diode has forward resistance of 20Ω and infinite backward resistance. Resistors R1 = R2 = R3 = 50Ω. Battery voltage is 6 V . The current through R3 is : (1) 50 mA (2) 100 mA (3) 60 mA (4) 25 mA

Q30.The I −V characteristics of an LED is: JEE Main 2013 (07 Apr) JEE Main Previous Year Paper (1) (2) (3) (4)

Q30.If a carrier wave c(t) = A sin ωct is amplitude modulated by a modulator signal m(t) = A sin ωmt then the equation of modulated signal [Cm(t)] and its modulation index are respectively (1) Cm(t) = A (1 + sin ωmt) sin ωct and 2 (2) Cm(t) = A (1 + sin ωmt) sin ωmt and 1 (3) Cm(t) = A (1 + sin ωmt) sin ωct and 1 (4) Cm(t) = A (1 + sin ωct) sin ωmt and 2

Q30.Correct set up to verify Ohm's law is : (1) (2) (3) (4)

Q30.Which of the following modulated signal has the best noise-tolerance ? (1) Long-wave (2) Short-wave (3) Medium-wave (4) Amplitude-modulated Q31. 6 litres of an alkene require 27 litres of oxygen at constant temperature and pressure for complete combustion. The alkene is : (1) Ethene (2) Propene (3) 1−Butene (4) 2−Butene

Q31.In an atom how many orbital(s) will have the quantum numbers; n = 3, l = 2 and ml = +2 ? (1) 5 (2) 3 (3) 1 (4) 7

Q31.The molarity of a solution obtained by mixing 750 mL of 0. 5(M) HCl with 250 mL of 2(M) HCl will be (1) 1. 75 M (2) 0. 975 M (3) 0. 875 M (4) 1. 00 M

Q31.Number of atoms in the following samples of substances is largest in: (1) 4.0 g of hydrogen (2) 71.0 g of chlorine (3) 127.0 g of iodine (4) 48.0 g of magnesium

Q31.The density of 3M solution of sodium chloride is 1.252 g mL−1 . The molality of the solution will be : ( molar mass, NaCl = 585 g mol−1) (1) 260 m (2) 2.18 m (3) 2.79 m (4) 3.00 m