Asystem that uses the reflection of underwater sound waves to detect objects.

1. sounds
2. ultrasound
3. sonar
4. refraction

3-Sonar

Explanation:

Sonar system is used to detect the under water objects by using the deflection of sound waves.

Sonar is an acronym of Sound navigation ranging.Two types of sonar sets are used for working: active and passive. The active sonar system pushes out sound signals called pings, and then absorbs the return sound echo. Passive sound sets obtain sound echoes without transmitting their actual sound signals. Submarines are using sonar to track other vessels.    

gas and liquid

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.