Assertion Path of a charged particle in uniform magnetic field cannot be a parabola, if no other forces (other than magnetic force) are acting on the particle.
Reason For parabolic path, a constant acceleration is required.

Options

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

Answer

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

### Step 1: Understand the Assertion
The assertion states that the path of a charged particle in a uniform magnetic field cannot be a parabola if no other forces (other than magnetic force) are acting on the particle.

- In a uniform magnetic field, a charged particle experiences a magnetic force that is always perpendicular to its velocity. This results in circular motion if the velocity is perpendicular to the magnetic field. If the velocity has a component parallel to the magnetic field, the particle will move in a helical path.
- Since neither circular nor helical paths can be parabolic, the assertion is **true**.

### Step 2: Understand the Reason
The reason states that a constant acceleration is required for a parabolic path.

- A parabolic path can be described by the equation \(y = ax^2 + bx + c\), which represents a quadratic function. For a projectile motion (which is a common example of a parabolic path), the vertical motion is influenced by gravity, which provides a constant acceleration downwards.
- However, it is also possible to have a parabolic path where the acceleration is not constant, depending on the equations of motion used. Thus, the statement that "for a parabolic path, a constant acceleration is required" is **false**.

### Step 3: Conclusion
Based on the analysis:
- The assertion is **true**: The path of a charged particle in a uniform magnetic field cannot be a parabola.
- The reason is **false**: A parabolic path does not necessarily require constant acceleration.

### Final Answer
The correct answer is that the assertion is true, but the reason is false.

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