Submarine Communication

The video discusses the challenges of communicating with submarines underwater due to the ocean's salt concentration affecting radio waves. It explains that while radio waves used on land are ineffective underwater, very low frequency (VLF) and extremely low frequency (ELF) radio waves are used for submarine communication. VLF waves can penetrate up to 20 meters underwater, allowing communication when submarines are near the surface. For greater depths, ELF waves are used, which have very long wavelengths but require large transmitters, making them suitable only for one-way communication from base to submarine. Due to their low frequency, ELF waves carry limited information, often just a command to surface.

What is the primary challenge in sending messages to submarines underwater?

• The ocean currents disrupt radio waves.

• Submarines do not have communication devices.

• Submarines are too deep to receive any signals.

• The ocean's salt concentration affects electromagnetic waves.

What frequency range do Very Low Frequency (VLF) radio waves fall into?

• 300 to 3000 kilohertz

• 3 to 30 megahertz

• 3 to 30 kilohertz

• 30 to 300 kilohertz

How deep can VLF radio waves penetrate into the ocean?

• 10 meters

• 50 meters

• 100 meters

• 20 meters

What is the typical frequency range used by submarines for ELF communication?

• 300 to 3000 Hertz

• 80 to 120 Hertz

• 40 to 80 Hertz

• 3 to 30 Hertz

Why is ELF communication one-way from the base to the submarine?

• ELF waves are too weak to send back.

• Submarines are not equipped with ELF receivers.

• ELF waves are too fast to be received by submarines.

• Submarines cannot carry large transmitters needed for ELF waves.