Answer :
Final answer:
In Plano mode (sleeve down), the light beam becomes wide due to the effect of diffraction, which causes light waves to spread out from their original path. Hence the correct option is (b).
Explanation:
The question you've asked relates to the behavior of light when it passes through different configurations, particularly focusing on what happens in Plano mode.
In Plano mode, with the sleeve down, the behavior of light is influenced by phenomena like diffraction, which causes light to spread out.
This spreading out is a fundamental characteristic of light waves due to their wave nature, particularly emphasized through diffraction where light passes through a slit or around obstacles, leading to a spreading out that can be described as diffraction.
Interestingly, when light passes through a single slit, it is diffracted in all directions and can interfere constructively or destructively depending on the angle, which significantly impacts the path and shape of the light beam.
Based on the principles of physics, when light beams spread out, they fail to remain narrow due to diffraction.
Therefore, the most accurate description of the light beam in Plano mode (sleeve down) is not narrow, circular, or square, but rather, it is wide because of the spreading effect of diffraction on the light waves.
