Which device detects objects using radio waves?

• A. Displays GPS position on electronic chart
• B. Transmits vessel identity
• C. Detects objects using radio waves
• D. Emergency beacon

Answer: (C)

Detecting objects with radio waves is the function of radar. Radar works by emitting radio waves and listening for their echoes, which lets you determine the distance and direction to objects like other boats or land; it helps you see around you even in poor visibility. That description matches the choice that states it detects objects using radio waves, so it’s the best answer.

The other options describe different systems: GPS displays your location by satellite signals, not by sensing surrounding objects; transmitting vessel identity refers to AIS, which broadcasts your own information rather than detecting others; and an emergency beacon is used to send a distress signal to responders, not to scan the environment.