You are imaging a tissue using a system operating a 1 MHz. If you double the ultrasonic frequency, what happens to the power of the returning scattered signal?

For most of the tissues, the attenuation or loss is proportional to the frequency.

Explanation:

So,If double the frequency,attenuation or loss also increases.So, the returning scattered signal power will decrease with increase in frequency.The amount by which it will decrease depends on the specific tissue.