Diffraction bends waves around obstacles

Steps:

• The hill blocks direct line-of-sight transmission of TV signals, which are electromagnetic waves.
• Waves can interact with obstacles in ways that allow propagation beyond the barrier.
• Diffraction specifically causes waves to spread and bend around edges of the hill.
• This bending enables the signal to reach the house despite the obstruction.

Why B is correct:

• Diffraction is the bending of waves around obstacles or through apertures, as described by Huygens' principle, allowing TV signals to curve over the hill into the shadow region.

Why the others are wrong:

• A. Coherence maintains phase relationships between waves but does not explain bending around barriers.
• C. Interference occurs when waves overlap and combine but requires waves to already reach the location.
• D. Reflection redirects waves off surfaces, but the hill's position would scatter signals away from the house rather than toward it.

Final answer: B