To solve the question regarding the assertion (A) and reason (R) in the context of Bohr's model, we will analyze both statements step by step.
### Step 1: Understanding the Assertion (A)
The assertion states that in Bohr's model, the frequency of revolution of an electron in its orbit is not connected to the frequency of the spectral line for smaller principal quantum numbers (n).
In Bohr's model, the frequency of revolution \( f \) of an electron in its orbit can be expressed as:
\[
f = \frac{Z^2 e^4 m}{4 \pi \epsilon_0^2 h^3 n^3}
\]
where \( Z \) is the atomic number, \( e \) is the charge of the electron, \( m \) is the mass of the electron, \( \epsilon_0 \) is the permittivity of free space, and \( h \) is Planck's constant.
For smaller values of \( n \), the energy levels are more widely spaced, and the transitions between these levels do not have a direct correlation with the frequency of revolution. Thus, the assertion is correct.
### Step 2: Understanding the Reason (R)
The reason states that for transitions between large quantum numbers, the frequency of revolution of an electron in its orbit is connected to the frequency of the spectral line, as per Bohr's Correspondence Principle.
According to Bohr's Correspondence Principle, as the quantum number \( n \) becomes very large, the energy levels become closer together, and the frequency of the emitted or absorbed radiation during transitions between these levels approaches the frequency of revolution of the electron.
For large \( n \), the relationship can be approximated as:
\[
f \approx \frac{Z^2}{n^3} f_0
\]
where \( f_0 \) is a constant. This indicates that the frequency of revolution does indeed relate to the spectral line frequency for large quantum numbers, making the reason correct.
### Conclusion
Both the assertion (A) and the reason (R) are correct. The assertion correctly states that for smaller \( n \), the frequencies are not connected, while the reason correctly states that for larger \( n \), they are connected.
### Final Answer
Both A and R are correct, and R is the correct explanation of A.
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