NEET Physics: Atoms and Nuclei — Practice Set 5

Q1. The radius of the first orbit in a hydrogen atom is \( 5.3 \times 10^{-11} \, \text{m} \). What is the circumference of the fourth orbit?

A. \( 5.33 \times 10^{-9} \, \text{m} \)
B. \( 3.0 \times 10^{-9} \, \text{m} \)
C. \( 1.33 \times 10^{-9} \, \text{m} \)
D. \( 2.12 \times 10^{-9} \, \text{m} \)

Q2. Which of the following statements is correct about Thomson’s model of the atom?

A. Positive charge is spread uniformly with electrons embedded in it
B. Positive charge is concentrated in a small nucleus
C. Electrons orbit the nucleus like planets
D. Atom consists of discrete energy levels

Q3. In the Bohr model, what is the ground state of a hydrogen atom?

A. State with \( n = 2 \)
B. State with zero energy
C. State with \( n = 1 \)
D. State with infinite radius

Q4. In Rutherford’s scattering experiment, what fraction of alpha-particles scatter by more than 90° out of 8000 incident particles?

A. 0.000125
B. 0.0014
C. 0.01
D. 0.00025

Q5. An electron in a hydrogen atom has a speed of \( 2.2 \times 10^6 \, \text{m/s} \) in the first orbit. What is its kinetic energy? (Mass of electron = \( 9.1 \times 10^{-31} \, \text{kg} \), 1 eV = \( 1.6 \times 10^{-19} \, \text{J} \))

A. 13.6 eV
B. 6.8 eV
C. 27.2 eV
D. 3.4 eV

Q6. What is the total energy of an electron in the \( n = 5 \) state of a hydrogen atom? (Use \( E_n = -\frac{13.6}{n^2} \, \text{eV} \))

A. -1.51 eV
B. -0.544 eV
C. -3.4 eV
D. -0.85 eV

Q7. What is the wavelength of the photon emitted when an electron in a hydrogen atom drops from \( n = 3 \) to \( n = 2 \)? (Use \( h = 6.6 \times 10^{-34} \, \text{J·s} \), \( c = 3 \times 10^8 \, \text{m/s} \), 1 eV = \( 1.6 \times 10^{-19} \, \text{J} \))

A. \( 4.86 \times 10^{-7} \, \text{m} \)
B. \( 5.12 \times 10^{-7} \, \text{m} \)
C. \( 6.12 \times 10^{-7} \, \text{m} \)
D. \( 6.56 \times 10^{-7} \, \text{m} \)

Q8. Which of the following is a key feature of Bohr’s model for the hydrogen atom?

A. Electrons have quantized angular momentum
B. Electrons emit radiation continuously
C. Positive charge is distributed uniformly
D. Nucleus orbits the electrons

Q9. In Rutherford’s model, what provides the centripetal force for an electron orbiting the nucleus in a hydrogen atom?

A. Gravitational force
B. Magnetic force
C. Electrostatic force
D. Nuclear force

Q10. In Rutherford’s model, what is the order of magnitude of the ratio of the atomic size to the nuclear size?

A. \( 10^3 \)
B. \( 10^4 \)
C. \( 10^5 \)
D. \( 10^6 \)

Physics — Atoms and Nuclei

Set 5 of 22

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The radius of the first orbit in a hydrogen atom is \( 5.3 \times 10^{-11} \, \text{m} \). What is the circumference of the fourth orbit?

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