🔍 Key Concepts

• How sound waves behave in water and what affects their strength or loss • What the fathometer’s gain control actually does to the echo signal • Which environmental factor changes the acoustic impedance or clarity of the returning echo the most

💭 Think About

• Think about which option would most directly affect how strong the echo is when it returns from the bottom to the transducer • Consider whether each factor changes how much sound is absorbed or scattered before it comes back • Ask yourself: which factor can vary the most, over short distances or different locations, in a way that would cause you to adjust gain often?

✅ Before You Answer

• For each choice, ask: does this primarily affect the speed of sound, or the strength/clarity of the echo? • Consider which factor a navigator would notice changing most when moving between different bottom conditions or different water masses • Verify in your mind: which factor would make the bottom echo appear weak or fuzzy, forcing you to increase gain to see it clearly?