Partial Reflection and Refraction at Air-Glass Interface

Steps:

• Identify the incident ray from air hitting the flat face of the semi-circular block.
• Apply law of reflection: reflected ray angle equals incident angle to normal.
• Apply Snell's law: refracted ray bends toward normal in denser glass (n_air < n_glass).
• Select diagram showing both rays emerging correctly from interface.

Why D is correct:

• It shows reflected ray at equal angle to incident ray and refracted ray bent toward normal, per laws of reflection and refraction.

Why the others are wrong:

• A: Omits partial reflection, showing only refraction.
• B: Refracted ray bends away from normal, violating Snell's law for denser medium.
• C: Reflected ray angle unequal to incident angle, breaking law of reflection.

Final answer: D