Atoms practice · Medium

Option A ($T_n \propto \frac{{n^3}}{{Z^2}}$) is correct because the time period is proportional to n cubed divided by Z squared, derived from Bohr's model.

Option B ($3 \times {10^8}m/s$) is correct because X-rays are electromagnetic waves and travel at the speed of light.

Option C is correct because Bohr's third postulate correctly states the quantization of angular momentum, but the linear momentum is not directly quantized in the same way.

Option C ($5 \mathrm{~Hz}$) is correct because it is calculated using the formula for the frequency of a standing wave in a string fixed at both ends.

Option A ($2\;\mathop A\limits^ \circ$) is correct because X-rays with shorter wavelengths have greater penetrating power.

Option B is correct because both the assertion and reason are true, but the reason does not correctly explain the assertion. The deviation is small because the alpha particle is far from the nucleus, and the impact parameter is defined as the perpendicular distance.

Option C ($U = 2E$) is correct because the potential energy is twice the total energy in magnitude and has the same sign.

Option B (Mechanical energy) is correct because under a conservative force, the total mechanical energy (kinetic + potential) is conserved.