\[ \therefore E \propto \frac{Z^2}{n^2} \] Energy of the 2^{nd} orbit: \[ E_2 = \frac{-13.6}{4} = -3.4\, \text{eV} \] \[ \Delta E_{2 \to 1} = 10.2\, \text{eV} \] So, only possible transition is from: \[ n = 2 \text{ to } n = 1 \]
To determine the number of spectral lines emitted when an electron in a hydrogen atom transitions after being excited, we first need to understand the given conditions. A hydrogen atom in the ground state (\(n=1\)) is excited with an energy of 10.2 eV.
The energy difference between the ground state and the first excited state (\(n=2\)) in a hydrogen atom is approximately 10.2 eV. When an electron is given exactly 10.2 eV of energy, it transitions from \(n=1\) to \(n=2\).
Once the electron is in the excited state \(n=2\), it can only transition back to \(n=1\) because there are no other lower energy levels that correspond to the given energy input. The transition thus results in the emission of energy in the form of a photon, corresponding to a single spectral line.
Based on this understanding, the number of spectral lines emitted is:
Hence, the correct option is 1.
A black body is at a temperature of 2880 K. The energy of radiation emitted by this body with wavelength between 499 nm and 500 nm is U1, between 999 nm and 1000 nm is U2 and between 1499 nm and 1500 nm is U3. The Wien's constant, b = 2.88×106 nm-K. Then,

What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)