Partial Reflection and Refraction at Air-Glass Interface

Steps:

• Identify that partial reflection occurs when some light bounces off the boundary at equal angles to incidence, per law of reflection.
• Note refraction bends the transmitted ray toward the normal if entering denser medium like glass, per Snell's law.
• For a semi-circular block, the ray enters the flat face, showing both reflected ray in air and refracted ray inside the block.
• Select diagram depicting incident ray splitting into reflected (in air) and refracted (bent into block) paths without total internal reflection.

Why D is correct:

• Diagram D illustrates partial reflection with the reflected ray at equal angle to incidence and refraction bending toward the normal, obeying laws of reflection and Snell's law.

Why the others are wrong:

• A shows only refraction with no reflected ray, ignoring partial reflection.
• B depicts total internal reflection inside the block, not entry from air.
• C shows incorrect refraction away from normal, violating Snell's law for air-to-glass.

Final answer: D