A student standing in a hallway can clearly hear music coming from a room even though the door is almost closed, leaving only a narrow opening a few centimeters wide. When the same student shines a small red laser pointer toward the opening, virtually no light reaches the hallway beyond the doorframe, and a sharp shadow is observed.
Use principles of wave behavior to account for the difference between how the sound and the laser light propagate through (or around) the doorway opening.
(a) Describe the physical meaning of "geometric shadow" and contrast it with the phenomenon of diffraction.
(b) Explain why audible sound waves spread noticeably into the hallway while the laser light does not, explicitly referring to the relative magnitudes of the doorway width and the wavelengths involved.