A plane wavefront is propagating in a medium. Which of the following is true?

Options

A. It propagates parallel to itself
B. It can not propagate in the medium
C. It changes to spherical wavefront
D. It changes to cyclindrical wavefront

Answer

To solve the question regarding the propagation of a plane wavefront in a medium, let's analyze the properties of wavefronts and their behavior.

### Step-by-Step Solution:

1. **Understanding Wavefronts**: A wavefront is defined as the surface over which an oscillation has a constant phase. For a plane wavefront, all points on the wavefront are in phase and propagate in the same direction.

2. **Characteristics of Plane Wavefronts**: In a plane wavefront, the waves propagate parallel to each other. This means that the distance between any two adjacent wavefronts remains constant as they move through the medium.

3. **Propagation in a Medium**: A plane wavefront can propagate through various media, including air, water, and glass. The statement that a plane wavefront cannot propagate in a medium is incorrect since it can indeed travel through different media.

4. **Relation to Spherical and Cylindrical Wavefronts**: While a plane wavefront is characterized by parallel wavefronts, spherical wavefronts emanate from a point source and spread out in all directions. Cylindrical wavefronts occur when the waves propagate from a line source.

5. **Conclusion**: The correct statement regarding the propagation of a plane wavefront in a medium is that it propagates parallel to each other.

### Final Answer:
The correct option is that a plane wavefront propagates parallel to each other in a medium.

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