NEET Atoms and Nuclei — Set 9

Question 1

An electron beam of 12.0 eV excites a hydrogen atom in the ground state. What is the highest energy level reached? (Use $ E_n = -\frac{13.6}{n^2} \, \text{eV} $)

Accepted Answer

$ E_1 = -13.6 \, \text{eV} $. $ E_n = -13.6 + 12.0 = -1.6 \, \text{eV} $. $ -1.6 = -\frac{13.6}{n^2} \Rightarrow n^2 \approx 8.5 \Rightarrow n = 2 $ (since $ E_2 = -3.4 \, \text{eV} < -1.6 \, \text{eV} $).

Question 2

What is the role of the impact parameter in Rutherford’s alpha-particle scattering?

Accepted Answer

The impact parameter determines the scattering angle; a smaller impact parameter leads to a larger deflection due to closer approach to the nucleus.

Question 3

Which of the following statements is incorrect about de Broglie’s explanation of Bohr’s model?

Accepted Answer

De Broglie’s hypothesis supports quantization by proposing standing waves, not continuous waves, which fit an integer number of wavelengths into the orbit.

NEET Physics: Atoms and Nuclei — Practice Set 9

Q1. An electron beam of 12.0 eV excites a hydrogen atom in the ground state. What is the highest energy level reached? (Use \( E_n = -\frac{13.6}{n^2} \, \text{eV} \))

Q2. What is the role of the impact parameter in Rutherford’s alpha-particle scattering?

Q3. Which of the following statements is incorrect about de Broglie’s explanation of Bohr’s model?

Q4. The radius of the first orbit in a hydrogen atom is \( 5.3 \times 10^{-11} \, \text{m} \). What is the radius of the fifth orbit?

Q5. In the Bohr model, what is the ratio of the radius of the \( n = 5 \) orbit to the \( n = 1 \) orbit?

Q6. What is the speed of an electron in the \( n = 4 \) orbit of a hydrogen atom if its speed in \( n = 1 \) is \( 2.2 \times 10^6 \, \text{m/s} \)?

Q7. In a hydrogen atom, the total energy of the electron in the ground state is -13.6 eV. What is its kinetic energy?

Q8. What limitation of Bohr’s model prevents it from explaining the spectrum of helium?

Q9. What is the energy of a photon emitted when an electron drops from \( n = 5 \) to \( n = 4 \) in a hydrogen atom? (Use \( E_n = -\frac{13.6}{n^2} \, \text{eV} \))

Q10. In Rutherford’s nuclear model, why do most alpha-particles pass through the gold foil without deflection?