Please help with these tysm

What happens to light waves from a star as the star moves away from earth?

The current in a hair dryer measures 11 amps. the resistance of the hair dryer is 12 ohms. what is the voltage?unit:

Waves are used in many practical applications to support work, entertainment, and health. one example is the use of ultrasound imaging to safely track the development of a growing fetus. what is a specific example of a practical application of waves in medicine, entertainment, safety, or other fields? provide a brief explanation of how the properties of waves are useful to that application.