NEET Practice Questions

Explanation: The magnetic field within the iron is given by; \(B=\mu_0(H+M)\). Since the iron is already saturated, there’s no more room for additional alignment of magnetic domains, and \(M\) (the magnetization of the material) remains constant. The magnetization of the given material is much larger than the magnetic intensity. Therefore, if the current is increased further, the magnetic field within the iron will increase slightly.
Hence, option (2) is the correct answer.
 

Step: Find the relation between the energy levels corresponding to the hydrogen atom and \(He^+\)– ion.
\(E_{n,H}=-\frac{13.6}{n^2}~\text{eV}\)
\(E_{n,He^+}=-\frac{13.6\times 2^2}{n^2}~\text{eV}\\ E_{2n,He^+}=-\frac{13.6\times 2^2}{(2n)^2}~\text{eV}=-\frac{13.6}{n^2}~\text{eV}=E_{n,H}\)
The energy level corresponding to the  \(n^{\text{th}}\) quantum number of the  \(H\)-atom has the same value as the  \(2n^{\text{th}}\) level of the  \(He^{+}\)-ion. Therefore, the energy of the photon causing the \(n=2\rightarrow4\) transition in the  \(He^+\)-ion is equal to the one causing the  \(n=1\rightarrow2\) transition in the  \(H\) -atom.
 Hence, option (1) is the correct answer.