Modern Physics Mock Tests

A radioactive nucleus decays by alpha emission to a daughter nucleus which then decays by beta emission. If the parent nucleus has atomic number Z and mass number A, the atomic number and mass number of the final nucleus are respectively:

In a hydrogen atom, an electron transitions from the n = 4 energy level to the n = 2 energy level. The wavelength of the emitted photon is closest to (R_H = 1.097 × 10⁷ m⁻¹):

A radioactive substance has a half-life of 5 years. The fraction of nuclei remaining after 15 years is:

Energy of photon: E = hc/λ = (6.63 × 10⁻³⁴)(3 × 10⁸)/(400 × 10⁻⁹) = 4.97 × 10⁻¹⁹ J = 3.11 eV. K_max = E - φ = 3.11 - 2.0 = 1.11 eV ≈ 1.1 eV.

In a transistor, the current amplification factor β = 50. If the collector current changes by 2 mA, the change in base current is:

A photon of energy 4.5 eV strikes a metal surface of work function 2.0 eV. The stopping potential is:

The de Broglie wavelength of an electron accelerated through a potential difference of 100 V is approximately:

The binding energy per nucleon is maximum for: