Assertion (A) : p orbital is dumb- bell shaped
Reason (R ) :Electron presents in p orbital can have any one of three value of magnetic quantum number i.e. `0,+1, or - 1`

Options

A. If both (A) and (R ) correct and (R ) is the correct explanation for (A)
B. If both (A) and (R ) correct and (R ) is the correct explanation for (A)
C. If (A) is correct but (R ) is incorrect
D. If (A) is incorrect but (R ) is correct

Explanation

To solve the question, we will analyze both the assertion and the reason provided and determine their correctness and relationship.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "p orbital is dumbbell shaped."
- This is a well-known fact in chemistry. The p orbitals have a characteristic dumbbell shape, which can be visualized as two lobes on either side of the nucleus, with a node at the nucleus.

**Conclusion**: The assertion is **correct**.

2. **Understanding the Reason (R)**:
- The reason states that "Electron present in p orbital can have any one of three values of magnetic quantum number i.e. 0, +1, or -1."
- The magnetic quantum number (m_l) for p orbitals can indeed take the values -1, 0, and +1. This corresponds to the three different orientations of the p orbitals (p_x, p_y, and p_z).

**Conclusion**: The reason is also **correct**.

3. **Analyzing the Relationship**:
- The assertion is about the shape of the p orbital, while the reason discusses the possible values of the magnetic quantum number for electrons in those orbitals.
- Although both statements are correct, the reason does not explain why the p orbital has a dumbbell shape. The shape is a result of the angular momentum of the electrons and the mathematical solutions to the Schrödinger equation, not merely the values of the magnetic quantum number.

**Conclusion**: The reason is **not a correct explanation** of the assertion.

4. **Final Answer**:
- Since both the assertion and reason are correct, but the reason does not explain the assertion, the correct option is:
- **B**: Both A and R are correct, but R is not the correct explanation of A.