1. The receiving sensitivity level of a hydrophone is -80 dB re 1 V/ubar. a) Express this sensitivity level re 1 V/uPa. (1 pt) b) What will be the output voltage if the pressure level of the field is 80 dB re 1 pbar? (1pt) 2. Explain what is meant by the thermal index (TI) and the mechanical index (MI), as displayed on the screens of some scanners. How are these numbers meant to help the operator assess the possible hazard risk associated with a scan? (2 pts)