Practice Questions

Q17.An electron of mass me and a proton of mass mP are accelerated through the same potential difference. The ratio of the de-Broglie wavelength associated with the electron to that with the proton is (1) mP (2) 1 me mp (3) √mpme (4) me

Q17.For a series LCR circuit with R = 100 Ω, L = 0. 5 mH and C = 0. 1 pF connected across 220 V −50 Hz AC supply, the phase angle between current and supplied voltage and the nature of the circuit is: (1) 0°, resistive circuit (2) ≈90°, predominantly inductive circuit (3) 0°, resonance circuit (4) ≈90°, predominantly capacitive circuit →

Q17.The de-Broglie wavelength of a particle having kinetic energy E is λ. How much extra energy must be given to this particle so that the de-Broglie wavelength reduces to 75% of the initial value? (1) E (2) 7E 9 (3) 16E (4) E 9 9

Q17.For an electromagnetic wave travelling in free space, the relation between average energy densities due to electric (Ue) and magnetic (Um) fields is : (1) Ue = Um (2) Ue > Um (3) Ue < Um (4) Ue ≠Um

Q17.The expected graphical representation of the variation of angle of deviation ' δ ' with angle of incidence 'i' in a prism is : (1) (2) (3) (4)

Q17.Consider two separate ideal gases of electrons and protons having same number of particles. The temperature of both the gases are same. The ratio of the uncertainty in determining the position of an electron to that of a proton is proportional to: 𝑚𝑝 𝑚𝑝 (1) (2) √ 𝑚𝑒 𝑚𝑒 (3) 𝑚𝑝 32 (4) 𝑚𝑒 √ 𝑚𝑝 𝑚𝑒 JEE Main 2021 (31 Aug Shift 2) JEE Main Previous Year Paper

Q18.A radioactive material decays by simultaneous emissions of two particles with half lives of 1400 years and 700 years, respectively. What will be the time after the which one third of the material remains ? (Take ln 3 = 1. 1 ) (1) 1110 years (2) 700 years (3) 340 years (4) 740 years

Q18.The half-life of 198Au is 3 days. If atomic weight of 198Au is 198 g mol-1, then the activity of 2 mg of 198Au is [in disintegration second-1]: (1) 2 . 67 × 1012 (2) 6 . 06 × 1018 (3) 32 . 36 × 1012 (4) 16 . 18 × 1012

Q18.The atomic hydrogen emits a line spectrum consisting of various series. Which series of hydrogen atomic spectra is lying in the visible region? (1) Brackett series (2) Paschen series (3) Lyman series (4) Balmer series

Q18.A sample of a radioactive nucleus A disintegrates to another radioactive nucleus B, which in turn disintegrates to some other stable nucleus C. Plot of a graph showing the variation of number of atoms of nucleus B vesus time is : (Assume that at t = 0, there are no B atoms in the sample) (1) (2) (3) (4)

Q18.At time t = 0 , a material is composed of two radioactive atoms A and B , where NA(0) = 2NB(0) The decay constant of both kind of radioactive atoms is λ . However, A disintegrates to B and B disintegrates to C . Which of the following figures represents the evolution of NB(t) with respect to time t? NB(0) (1) (2) (3) (4)

Q18.The angle of deviation through a prism is minimum when (A) Incident ray and emergent ray are symmetric to the prism (B) The refracted ray inside the prism becomes parallel to its base (C) Angle of incidence is equal to that of the angle of emergence (D) When angle of emergence is double the angle of incidence Choose the correct answer from the options given below : (1) Statements (A),(B) and (C) are true (2) Only statement (D) is true (3) Only statements (A) and (B) are true (4) Statements (B) and (C) are true

Q18.A 5 V battery is connected across the points X and Y . Assume D1 and D2 to be normal silicon diodes. Find the current supplied by the battery if the +ve terminal of the battery is connected to point X . (1) ~0. 86 A (2) ~0. 5 A (3) ~1. 5 A (4) ~0. 43 A

Q18.A ray of light entering from air into a denser medium of refractive index 4 , as shown in figure. 3 The light ray suffers total internal reflection at the adjacent surface as shown. The maximum value of angle θ should be equal to: JEE Main 2021 (25 Jul Shift 2) JEE Main Previous Year Paper (1) sin−1 √73 (2) sin−1 √54 (3) sin−1 √74 (4) sin−1 √53

Q18.Given below are two statements: Statement I: Two photons having equal linear momenta have equal wavelengths. Statement II: If the wavelength of the photon is decreased, then the momentum and energy of a photon will also decrease. In the light of the above statements, choose the correct answer from the options given below. (1) Both Statement I and Statement II are false (2) Both Statement I and Statement II are true (3) Statement I is true but Statement II is false (4) Statement I is false but Statement II is true

Q18.The truth table for the following logic circuit is : (1) (2) (3) (4)

Q18.A monochromatic neon lamp with wavelength of 670. 5 nm illuminates a photo-sensitive material which has a stopping voltage of 0. 48 V . What will be the stopping voltage if the source light is changed with another source of wavelength of 474. 6 nm ? (1) 0. 24 V (2) 1. 5 V (3) 1. 25 V (4) 0. 96 V

Q18.In a Young's double slit experiment two slits are separated by 2 mm and the screen is placed one meter away. When a light of wavelength 500 nm is used, the fringe separation will be : (1) 1 mm (2) 0. 50 mm (3) 0. 75 mm (4) 0. 25 mm

Q18.A free electron of 2 . 6 eV energy collides with a H+ ion. This results in the formation of a hydrogen atom in the first excited state and a photon is released. Find the frequency of the emitted photon. ℎ= 6 . 6 × 10-34 J s (1) 9 . 0 × 1027 MHz (2) 1 . 45 × 109 MHz (3) 0 . 19 × 1015 MHz (4) 1 . 45 × 1016 MHz

Q18.Which level of the single ionized carbon has the same energy as the ground state energy of hydrogen atom? (1) 1 (2) 6 (3) 4 (4) 8

Q18.The temperature of an ideal gas in three dimensions is 300 K . The corresponding de-Broglie wavelength of the electron approximately at 300 K is: 𝑚𝑒= mass of electron = 9 × 10-31 kg, ℎ= Planck constant = 6 . 6 × 10-34 J s, 𝑘𝐵= Boltzmann constant = 1 . 38 × 10-23 J K-1 (1) 2 . 26 nm (2) 3 . 25 nm (3) 8 . 46 nm (4) 6 . 26 nm

Q18.The recoil speed of a hydrogen atom after it emits a photon in going from n = 5 state to n = 5 state will be (1) 4. 17 m s−1 (2) 2. 19 m s−1 (3) 4. 34 m s−1 (4) 3. 25 m s−1

Q18. The logic circuit shown above is equivalent to : JEE Main 2021 (24 Feb Shift 2) JEE Main Previous Year Paper (1) (2) (3) (4)

Q18.The speed of electrons in a scanning electron microscope is 1 × 107 ms−1 . If the protons having the same speed are used instead of electrons, then the resolving power of scanning proton microscope will be changed by a factor of: (1) 1837 (2) 18371 (3) √1837 (4) 1 √1837

Q18.Identify the logic operation carried out by the given circuit: (1) OR (2) AND (3) NAND (4) NOR