Assertion : Wavefronts obtained from light emitted by a point source in an isotropic medium are always spherical.
Reason : Speed of light in isotropic medium is constant.

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 the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

To solve the question regarding the assertion and reason provided, we will analyze both statements step by step.

### Step 1: Understand the Assertion
The assertion states that "Wavefronts obtained from light emitted by a point source in an isotropic medium are always spherical."

- A point source emits light uniformly in all directions.
- In an isotropic medium, the properties of the medium are the same in all directions.
- Therefore, the light waves will propagate outward in a uniform manner, forming spherical wavefronts.

### Step 2: Understand the Reason
The reason states that "Speed of light in isotropic medium is constant."

- In an isotropic medium, the speed of light does not vary with direction.
- This uniform speed in all directions contributes to the formation of spherical wavefronts.
- Since the speed of light is constant, the wavefronts maintain a consistent shape as they expand outward.

### Step 3: Establish the Relationship
Now we need to establish the relationship between the assertion and the reason.

- The assertion is true because light from a point source in an isotropic medium indeed forms spherical wavefronts.
- The reason is also true because the speed of light in an isotropic medium is constant.
- Furthermore, the reason provides a correct explanation for the assertion, as the constant speed of light leads to the formation of spherical wavefronts.

### Conclusion
Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct answer is that both the assertion and the reason are true, and the reason is the correct explanation of the assertion.

### Final Answer
- **Assertion**: True
- **Reason**: True
- **Conclusion**: The reason is the correct explanation of the assertion.

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