Final answer:
Rescue aircraft use direction finding radio equipment to locate distress signals from ELTs. Extremely low frequency radio waves are employed for communicating with submarines because they can penetrate salt water, unlike higher frequency waves.
Step-by-step explanation:
Rescue aircraft often use direction finding (DF) radio equipment to locate the distress signals emitted from an aircraft's Emergency Locator Transmitter (ELT) during search and rescue missions. These DF systems are designed to identify the direction of a transmission and help rescuers pinpoint the position of the aircraft in distress. This is crucial in situations where time is of the essence and precise location is necessary to conduct an effective rescue operation.
Additionally, it's worth noting that extremely low frequency (ELF) radio waves are particularly useful for communication with submerged submarines, as they have the ability to penetrate salt water due to their longer wavelengths. Higher frequency waves, like those used in mobile phones, do not penetrate well through conductive mediums such as salt water. This is why ELF waves, which have a lower frequency and thus a longer wavelength, are used for communication with submarines.
This principle of wave penetration is akin to how ultrasound penetrates biological tissue, where longer wavelengths can travel further into the body. This knowledge is applied in various fields to ensure the reliability and safety of communications.