Assertion: During de-excitation from n=6 to n=3 , total six emission lines may be obtained.
Reason: From `n=n to n =1 total (n(n-1)/(2)` emission lines are obtained.

Options

A. If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
B. If both Assertion and Reason or true but Reason is not the correct explanation of Assertion.
C. If Assertion is true, but the Reason is false.
D. If Assertion is false but the Reason is true.

Explanation

To solve the question, we need to analyze both the assertion and the reason given.

### Step 1: Understand the Assertion
The assertion states that during the de-excitation from n=6 to n=3, a total of six emission lines may be obtained.

### Step 2: Determine the Number of Emission Lines
To find the number of emission lines when an electron transitions from a higher energy level (n1) to a lower energy level (n2), we can use the formula:
\[ \text{Number of emission lines} = \frac{(n_1 - n_2)(n_1 - n_2 + 1)}{2} \]
Here, \( n_1 = 6 \) and \( n_2 = 3 \).

### Step 3: Substitute Values into the Formula
Substituting the values into the formula:
\[ \text{Number of emission lines} = \frac{(6 - 3)(6 - 3 + 1)}{2} \]
Calculating this:
\[ = \frac{(3)(4)}{2} = \frac{12}{2} = 6 \]

### Step 4: Conclusion on Assertion
The assertion is correct because we calculated that there are indeed six emission lines when transitioning from n=6 to n=3.

### Step 5: Understand the Reason
The reason states that from n=n to n=1, the total number of emission lines is given by the formula:
\[ \text{Number of emission lines} = \frac{n(n-1)}{2} \]
This formula is indeed correct, but it specifically applies when transitioning to the ground state (n=1).

### Step 6: Analyze the Reason
In our case, since we are transitioning from n=6 to n=3, the reason does not directly apply to the assertion. The reason is true in general, but it does not explain the specific case of the assertion.

### Final Conclusion
Both the assertion and the reason are true, but the reason is not the correct explanation for the assertion. Therefore, the correct answer is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion.

### Answer:
Both assertion and reason are true, but the reason is not the correct explanation of the assertion.

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