Practice Questions

Q30.Radius of a certain orbit of hydrogen atom is 8.48Ã … . If energy of electron in this orbit is E/x. then x = _____ (Given a0 = 0.529Ã … , E = energy of electron in ground state).

Q30.In an experiment to measure the focal length ( 𝑓) of a convex lens, the magnitude of object distance ( 𝑥) and the image distance ( 𝑦) are measured with reference to the focal point of the lens. The 𝑦- 𝑥 plot is shown in figure. The focal length of the lens is _____cm .

Q30.The mass defect in a particular reaction is 0 . 4 g. The amount of energy liberated is 𝑛× 107 kW h, where 𝑛= _____. (speed of light = 3 × 108 m s-1)

Q30.A nucleus has mass number 𝐴1 and volume 𝑉1. Another nucleus has mass number 𝐴2 and volume 𝑉2. If 𝑉2 relation between mass number is 𝐴2 = 4𝐴1, then = _______. 𝑉1

Q30.A hydrogen atom changes its state from n = 3 to n = 2. Due to recoil, the percentage change in the wave length of emitted light is approximately 1 × 10−n . The value of n is_____. [Given Rhc = 13.6eV, hc = 1242eVnm, h = 6.6 × 10−34 J s mass of the hydrogenatom = 1.6 × 10−27 kg ] JEE Main 2024 (04 Apr Shift 1) JEE Main Previous Year Paper

Q30.In an alpha particle scattering experiment distance of closest approach for the α particle is 4.5 × 10−14 m . If target nucleus has atomic number 80 , then maximum velocity of α - particle is _______ ×105 m/s approximately. = 9 × 109 SI unit, mass of α particle = 6.72 × 10−27 kg) ( 4πϵ01

Q30.In Franck-Hertz experiment, the first dip in the current-voltage graph for hydrogen is observed at 10.2 V. The wavelength of light emitted by hydrogen atom when excited to the first excitation level is _________ nm . (Given hc = 1245eVnm, e = 1.6 × 10−19C ).

Q30.Hydrogen atom is bombarded with electrons accelerated through a potential different of V , which causes excitation of hydrogen atoms. If the experiment is being formed at T = 0 K. The minimum potential difference needed to observe any Balmer series lines in the emission spectra will be α V , where α = 10 _________.(Write the value to the nearest integer)

Q30.If Rydberg's constant is R, the longest wavelength of radiation in Paschen series will be 7𝑅, where 𝛼= ______.

Q30.An electron of hydrogen atom on an excited state is having energy En = −0. 85 eV. The maximum number of allowed transitions to lower energy level is _______.

Q30.When a hydrogen atom going from n = 2 to n = 1 emits a photon, its recoil speed is x5 m s−1 . Where x = _______. (Use: mass of hydrogen atom = 1. 6 × 10−27 kg , charge of electron e = 1. 6 × 10−19 C)

Q30.A particular hydrogen - like ion emits the radiation of frequency 3 × 1015 Hz when it makes transition from 𝑥 𝑛= 2 to 𝑛= 1 . The frequency of radiation emitted in transition from 𝑛=3 to 𝑛= 1 is × 1015 Hz, when 9 𝑥= _____.

Q30.A star has 100% helium composition. It starts to convert three 4He into one 12C via triple alpha process as 4He + 4He + 4He →12C + Q. The mass of the star is 2.0 × 1032 kg and it generates energy at the rate of 5.808 × 1030 W. The rate of converting these 4He to 12C is n × 1042 s−1 , where n is _________ [ Take, mass of 4He = 4.0026u, mass of 12C = 12u ]

Q1. If 𝑅, 𝑋𝐿 and 𝑋𝐶 represent resistance, inductive reactance and capacitive reactance. Then which of the following is dimensionless: 𝑅 (1) 𝑅 𝑋𝐿 𝑋𝐶 (2) √𝑋𝐿𝑋𝑐 𝑅 𝑋𝐿 (3) (4) 𝑅 𝑋𝐿𝑋𝑐 𝑋𝑐

Q1. When vector A = 2ˆi + 3ˆj + 2ˆk is subtracted from vector B, it gives a vector equal to 2ˆj. Then the magnitude of → vector B will be: (1) √5 (2) 3 (3) √6 (4) √33

Q1. Electric field in a certain region is given by →𝐸= 𝐴 ^i + 𝐵 ^j. The SI unit of 𝐴 and 𝐵 are : 𝑥2 𝑦3 (1) N m3 C-1; N m2 C-1 (2) N m2 C-1; N m3 C-1 (3) N m3 C; N m2 C (4) N m2 C; N m3 C

Q1. Match List I with List II List I List II A Torque I kg m–1 s–2 B Energy density II kg m s–1 C Pressure gradient III kg m–2 s–2 D Impulse IV kg m2 s–2 Choose the correct answer from the options given below : (1) A-IV, B-III, C-I, D-II (2) A-I, B-IV, C-III, D-II (3) A-IV, B-I, C-II, D-III (4) A-IV, B-I, C-III, D-II

Q1. In an experiment of measuring the refractive index of a glass slab using travelling microscope in physics lab, a student measures real thickness of the glass slab as 5. 25 mm and apparent thickness of the glass slab at 5. 00 mm . Travelling microscope has 20 divisions in one cm on main scale and 50 divisions on Vernier scale is equal to 49 divisions on main scale. The estimated uncertainty in the measurement of refractive index of the slab is x × 10−3 , where x is ______ 10

Q1. Given below are two statements : Statement I : Astronomical unit (Au), Parsec (Pc) and Light year (ly) are units for measuring astronomical distances. Statement II : Au < Parsec (Pc) < ly In the light of the above statements, choose the most appropriate answer from the options given below: (1) Both Statements I and Statements II are incorrect (2) Statements I is correct but Statements II is incorrect (3) Both Statements I and Statements II are correct (4) Statements I is incorrect but Statements II is correct

Q1. If two vectors P = ˆi + 2mˆj + mˆk and Q = 4ˆi −2ˆj + mˆk are perpendicular to each other. Then, the value of m will be (1) −1 (2) 2 (3) 3 (4) 1

Q1. Match List I with List II : List-I (Physical Quantity) List-II (Dimensional Formula) A Pressure gradient I [M0L2T−2] B Energy density II [M1L−1T−2] C Electric Field III [M1L−2T−2] D Latent heat IV [M1L1T−3A−1] Choose the correct answer from the options given below: (1) A-III, B-II, C-I, D-IV (2) A-II, B-III, C-IV, D-I (3) A-III, B-II, C-IV, D-I (4) A-II, B-III, C-I, D-IV

Q1. Match List I with List II List List II A Young's Modulus (Y ) I [ML–1 T –1] B Co-efficient of Viscosity (η) II [ML2 T –1] C Planck's Constant (h) III [ML–1 T –2] D Work Function (ϕ) IV [ML2 T–2] Choose the correct answer from the options given below: (1) A-II, B-III, C-IV, D-I (2) A-III, B-I, C-II, D-IV (3) A-I, B-III, C-IV, D-II (4) A-I, B-II, C-III, D-IV

Q1. If P = 3ˆi + √3ˆj + 2ˆk and Q = 4ˆi + √3ˆj + 2. 5ˆk then, the unit vector in the direction of P × Q is x is x 1 (√3ˆi +ˆj −2√3ˆk). The value of

Q1. A body is moving with constant speed, in a circle of radius 10 m. The body completes one revolution in 4 s. At the end of 3rd second, the displacement of body (in m) from its starting point is: (1) 30 (2) 15 π (3) 5 π (4) 10√2

Q1. Three forces F1 = 10 N, F2 = 8 N, F3 = 6 N are acting on a particle of mass 5 kg. The forces F2 and F3 are applied perpendicularly so that particle remains at rest. If the force F1 is removed, then the acceleration of the particle is (1) 7 m s–2 (2) 0. 5 m s–2 (3) 4. 8 m s–2 (4) 2 m s–2