Practice Questions

Q27.The wavelength of the radiation emitted is λ0 when an electron jumps from the second excited state to the first excited state of hydrogen atom. If the electron jumps from the third excited state to the second orbit of the hydrogen atom, the wavelength of the radiation emitted will be 20 x λ0 . The value of x is________.

Q27.A 12. 5 eV electron beam is used to bombard gaseous hydrogen at room temperature. The number of spectral lines emitted will be: (1) 1 (2) 4 (3) 2 (4) 3

Q27.A straight wire carrying a current of 14 A is bent into a semicircular arc of radius 2 . 2 cm as shown in the figure. The magnetic field produced by the current at the centre 𝑂 of the arc is ____ × 10 – 4 T JEE Main 2023 (10 Apr Shift 2) JEE Main Previous Year Paper

Q27.A radioactive element 24292X emits two α-particles, one electron and two positrons. The product nucleus is represented by 234PY . The value of P is ______. JEE Main 2023 (29 Jan Shift 1) JEE Main Previous Year Paper

Q27.An electron in a hydrogen atom revolves around its nucleus with a speed of 6. 76 × 106 m s–1 in an orbit of radius 0. 52 Å. The magnetic field produced at the nucleus of the hydrogen atom is _______ T.

Q27.An object is placed on the principal axis of convex lens of focal length 10 cm as shown. A plane mirror is placed on the other side of lens at a distance of 20 cm. The image produced by the plane mirror is 5 cm inside the mirror. The distance of the object from the lens is ____ cm.

Q27.A straight wire AB of mass 40 g and length 50 cm is suspended by a pair of flexible leads in uniform magnetic field of magnitude 0 . 40 T as shown in the figure. The magnitude of the current required in the wire to remove the tension in the supporting leads is _____ A. (Take 𝑔= 10 m s-2.

Q28.An inductor of 0 . 5 mH, a capacitor of 20 μF and resistance of 20 Ω are connected in series with a 220 V ac source. If the current is in phase with the emf, the amplitude of current of the circuit is √𝑥 A. The value of 𝑥 is-

Q28.Nucleus a having Z = 17 and equal number of protons and neutrons has 1. 2 MeV binding energy per nucleon. Another nucleus B of Z = 12 has total 26 nucleons and 1. 8 MeV binding energy per nucleons. The JEE Main 2023 (01 Feb Shift 2) JEE Main Previous Year Paper difference of binding energy of B and A will be ______ MeV.

Q28.In Young’s double slit experiment, two slits 𝑆1 and 𝑆2 are 𝑑 distance apart and the separation from slits to screen is 𝐷 (as shown in figure). Now if two transparent slabs of equal thickness 0 . 1 mm but refractive index 1 . 51 and 1 . 55 are introduced in the path of beam λ = 4000 Å from 𝑆1 and 𝑆2 respectively. The central bright fringe spot will shift by ________ number of fringes.

Q28.A 20 cm long metallic rod is rotated with 210 rpm about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field 0. 2 T parallel to the axis exists everywhere. The emf developed between the centre and the ring is _________ mV. JEE Main 2023 (15 Apr Shift 1) JEE Main Previous Year Paper (Take π = 227 )

Q28.A radio active material is reduced to 1 of its original amount in 3 days. If 8 × 10−3 kg of the material is left 8 after 5 days the initial amount of the material is (1) 40 g (2) 32 g (3) 64 g (4) 256 g

Q28.An insulated copper wire of 100 turns is wrapped around a wooden cylindrical core of the cross-sectional area 24 cm2. The two ends of the wire are connected to a resistor. The total resistance in the circuit is 12 Ω. If an externally applied uniform magnetic field in the core along its axis changes from 1 . 5 T in one direction to 1 . 5 T in the opposite direction, the charge flowing through a point in the circuit during the change of magnetic field will be _____ mC.

Q28.The energy released per fission of nucleus of 240X is 200 MeV . The energy released if all the atoms in 120 g of pure 240X undergo fission is _____ ×1025 MeV . (Given NA = 6 × 1023 )

Q28.In the circuit shown in the figure, the ratio of the quality factor and the band width is _____ s.

Q28.An ideal transformer with purely resistive load operates at 12 kV on the primary side. It supplies electrical energy to a number of nearby houses at 120 V . The average rate of energy consumption in the houses served by the transformer is 60 kW . The value of resistive load ( 𝑅𝑠) required in the secondary circuit will be _________mΩ .

Q28.A series LCR circuit is connected to an ac source of 220 V, 50 Hz. The circuit contain a resistance 𝑅= 100 Ω and an inductor of inductive reactance 𝑋𝐿= 79 . 6 Ω. The capacitance of the capacitor needed to maximize the average rate at which energy is supplied will be ______ μF.

Q28.A radioactive nucleus decays by two different process. The half life of the first process is 5 minutes and that of the second process is 30 s. The effective half-life of the nucleus is calculated to be 11α s. The value of α is ______.

Q28.Given below are two statements : Statement I : Stopping potential in photoelectric effect does not depend on the power of the light source. Statement II : For a given metal, the maximum kinetic energy of the photoelectron depends on the wavelength of the incident light. In the light of above statements, choose the most appropriate answer from the options given below. (1) Statement I is incorrect but statement II is correct (2) Both Statement I and Statement II are incorrect (3) Statement I is correct but statement II is incorrect (4) Both statement I and statement II are correct

Q28.A common example of alpha decay is 23892U →23490 Th +2 He4 + Q Given: 23892U = 238. 05060 u 23490Th = 234. 04360 u 42He = 4. 00260 u and 1u = 931. 5 MeVc2 The energy released (Q) during the alpha decay of 23892U is _____ MeV.

Q28.A nucleus with mass number 242 and binding energy per nucleon as 7. 6 MeV breaks into two fragment each with mass number 121. If each fragment nucleus has binding energy per nucleon as 8. 1 MeV, the total gain in binding energy is _______ MeV.

Q28.The magnetic field B crossing normally a square metallic plate of area 4 m2 is changing with time as shown in figure. The magnitude of induced emf in the plate during 𝑡= 2 s to 𝑡= 4 s, is _____ 𝑚𝑉.

Q28.If the binding energy of ground state electron in a hydrogen atom is 13. 6 eV , then, the energy required to remove the electron from the second excited state of Li 2+ will be: x × 10−1 eV . The value of x is _____.

Q28.A 1 m long metal rod 𝑋𝑌 completes the circuit as shown in figure. The plane of the circuit is perpendicular to the magnetic field of flux density 0 . 15 T. If the resistance of the circuit is 5 Ω, the force needed to move the rod in direction, as indicated, with a constant speed of 4 m s-1 will be _______10 – 3 N.

Q29.Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: Diffusion current in a p −n junction is greater than the drift current in magnitude if the junction is forward biased. Reason R: Diffusion current in a p −n junction is form the n-side to the p-side if the junction is forward biased. In the light of the above statements, choose the most appropriate answer from the options given below. (1) Both A and R are correct but R is NOT the (2) A is correct but R is not correct correct explanation of A (3) A is not correct but R is correct (4) Both A and R is correct and R is the correct explanation of A