Understanding the Fathometer

The question asks what a 'Fathometer' is used to measure. Let's examine the options provided.

A Fathometer is a specific instrument that utilizes the principles of sonar (Sound Navigation and Ranging) to determine the depth of water. It works by emitting sound waves downwards into the water and measuring the time it takes for the echo to return after bouncing off the seabed or a submerged object. The time delay, combined with the known speed of sound in water, allows the instrument to calculate the distance, which is the depth.

The unit of measurement commonly associated with a Fathometer is the 'fathom', which is a unit of depth equal to six feet or approximately 1.83 meters.

Analyzing the Options

• Earthquakes: Earthquakes are measured using seismographs, which detect and record seismic waves. A Fathometer is not used for this purpose.
• Rainfall: Rainfall is measured using a rain gauge, which collects and quantifies the amount of precipitation over a specific period. A Fathometer is unrelated to measuring rainfall.
• Ocean Depth: As explained above, a Fathometer is specifically designed to measure the depth of bodies of water, most commonly oceans, seas, and lakes. It is a standard tool used in hydrography and navigation.
• Sound Intensity: Sound intensity is measured using instruments like sound level meters (also known as decibel meters). While a Fathometer uses sound waves, it measures distance/depth, not the intensity or loudness of sound itself.

Based on the function of a Fathometer, its primary use is to measure ocean depth.

Summary of Instruments

Therefore, the 'Fathometer' is used to measure Ocean Depth.