Practice Questions

Q24.The first diffraction minimum due to the single slit diffraction is seen at θ = 30∘ for a light of wavelength 5000Å falling perpendicularly on the slit. The width of the slit is (1) 2.5 × 10−5 cm (2) 1.25 × 10−5 cm (3) 10 × 10−5 cm (4) 5 × 10−5 cm

Q24.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 : Davisson - germer experiment established the wave nature of electrons. Statement 2 : If electrons have wave nature, they can interfere and show diffraction. (1) Statement 1 is false, Statement 2 is true (2) Statement 1 is true, Statement 2 is false (3) Statement 1 is true, Statement 2 is the correct (4) Statement 1 is true, Statement 2 is true, explanation for statement 1 Statement 2 is not the correct explanation for statement 1.

Q25.Hydrogen atom is excited from ground state to another state with principal quantum number equal to 4. Then the number of spectral lines in the emission spectra will be (1) 2 (2) 3 (3) 5 (4) 6

Q25.Two polaroids have their polarizing directions parallel so that the intensity of a transmitted light is maximum. The angle through which either polaroid must be turned if the intensity is to drop by one-half is (1) 135∘ (2) 90∘ (3) 120∘ (4) 180∘

Q26.Ionisation energy of Li (Lithium) atom in ground state is 5.4eV . Binding energy of an electron in Li+ ion in ground state is 75.6eV . Energy required to remove all three electrons of Lithium (Li) atom is (1) 81.0eV (2) 135.4eV (3) 203.4eV (4) 156.6eV JEE Main 2012 (19 May Online) JEE Main Previous Year Paper

Q28.Which one of the following is the Boolean expression for NOR gate? –– (1) Y = A + B (2) Y = A ⋅B (3) Y = A ⋅B (4) Y = ¯A

Q29.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: A pure semiconductor has negative temperature coefficient of resistance. Statement 2: On raising the temperature, more charge carriers are released into the conduction band. (1) Statement 1 is false, Statement 2 is true. (2) Statement 1 is true, Statement 2 is false. (3) Statement 1 is true, Statement 2 is true, (4) Statement 1 is true, Statement 2 is true, Statement 2 is not a correct explanation of Statement 2 is the correct explanation of Statement 1. Statement 1.

Q29.A radar has a power of 1 Kw and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500 m. The maximum distance upto which it can detect object located on the surface of the earth (Radius of earth = 6.4 × 106 m ) is (1) 80 km (2) 16 km (3) 40 km (4) 64 km

Q30. N divisions on the main scale of a vernier calliper coincide with (N + 1) divisions of the vernier scale. If each division of main scale is ' a ' units, then the least count of the instrument is (1) a (2) Na (3) N+1 N × a (4) N+1a

Q30.The figure shows a combination of two NOT gates and a NOR gate. JEE Main 2012 (26 May Online) JEE Main Previous Year Paper The combination is equivalent to a (1) NAND gate (2) NOR gate (3) AND gate (4) OR gate

Q30.Broadcasting antennas are generally (1) vertical type (2) both vertical and horizontal type (3) omni directional type (4) horizontal type

Q3. A water fountain on the ground sprinkles water all around it. If the speed of water coming out of the fountain is v, the total area around the fountain that gets wet is : (1) π v4g2 (2) π2 v4g2 (3) π v2 (4) π v4g g2

Q11.A Carnot engine operating between temperatures T1 and T2 has efficiency 16 . When T2 is lowered by 62 K, its efficiency increases to 1 . Then T1 and T2 are, respectively : 3 (1) 372 K and 330 K (2) 330 K and 268 K (3) 310 K and 248 K (4) 372 K and 310 K

Q21.A boat is moving due east in a region where the earth's magnetic field is 5.0 × 10−5NA−1 m−1 due north and horizontal. The boat carries a vertical aerial 2 m long. If the speed of the boat is 1.50 ms−1 , the magnitude of the induced emf in the wire of aerial is : (1) 0.75mV (2) 0.50mV (3) 0.15mV (4) 1mV

Q27.Energy required for the electron excitation in Li++ from the first to the third Bohr orbit is : (1) 36.3eV (2) 108.8eV (3) 122.4eV (4) 12.1eV

Q29.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 : Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals. Statement-2 : The state of ionosphere varies from hour to hour, day to day and season to season. (1) Statement-1 is true, Statement-2 is true; (2) Statement-1 is true, Statement-2 is true; Statement-2 is the correct explanation of Statement-2 is not the correct explanation of Statement-1. Statement-1. (3) Statement- 1 is false, Statement- 2 is true. (4) Statement-1 is true, Statement-2 is false. JEE Main 2011 JEE Main Previous Year Paper

Q30.A screw gauge gives the following reading when used to measure the diameter of a wire. Main scale reading : 0 mm Circular scale reading : 52 divisions Given that 1 mm on main scale corresponds to 100 divisions of the circular scale. The diameter of wire from the above date is : (1) 0.052 cm (2) 0.026 cm (3) 0.005 cm (4) 0.52 cm

Q1. The respective number of significant figures for the numbers 23.023, 0.0003 and 2.1 × 10−3 are (1) 5, 1, 2 (2) 5, 1, 5 (3) 5, 5, 2 (4) 4, 4, 2

Q9. For a particle in uniform circular motion the acceleration →a at a point P(R, θ) on the circle of radius R is (here θ is measured from the x-axis) (1) −v2R cos θ^i + v2R sin θ^j (2) −v2R sin θ^i + v2R cos θ^j (3) −v2R cos θ^i −v2R sin θ^j (4) v2R ^i + v2R ^j

Q10.A ball is made of a material of density ρ where ρoil < ρ < ρwater with ρoil and ρwater representing the densities of oil and water, respectively. The oil and water are immiscible. If the above ball is in equilibrium in a mixture of this oil and water, which of the following pictures represents its equilibrium position? JEE Main 2010 JEE Main Previous Year Paper (1) (2) (3) (4)

Q24.An initially parallel cylindrical beam travels in a medium of refractive index μ(I) = μ0 + μ2I , where μ0 and μ2 are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius. The initial shape of the wave front of the beam is (1) convex (2) concave (3) convex near the axis and concave near the (4) planar periphery

Q30. The combination of gates shown below yields (1) OR gate (2) NOT gate (3) XOR gate (4) NAND gate

Q1. A particle has an initial velocity 3^i + 4^j and an acceleration of 0.4^i + 0.3^j. Its speed after 10 s is (1) 10 units (2) 7√2 units (3) 7 units (4) 8.5 units

Q4. The height at which the acceleration due to gravity becomes g (where g = the acceleration due to gravity on 9 the surface of the earth) in terms of R, the radius of the earth is (1) 2R (2) R √2 (3) R (4) √2R 2

Q6. A long metallic bar is carrying heat from one of its ends to the other end under steady-state. The variation of temperature θ along the length x of the bar from its hot end is best described by which of the following figure. (1) (2) (3) (4) JEE Main 2009 JEE Main Previous Year Paper