Final answer:
Weld discontinuities in ultrasonic testing are typically assessed based on the signal amplitude. The time of reflection of sound waves in nondestructive testing defines the quality of the coating on frying pans. The student's question can be solved by calculating the velocity of the ultrasonic wave and subsequently determining the reflection time for a specific coating thickness.
Step-by-step explanation:
As a general rule, weld discontinuities detected by ultrasonic testing are accepted or rejected on the basis of signal amplitude. The method described as part of the ultrasonic nondestructive testing involves sending sound waves through the nonstick coating of a frying pan and measuring the time it takes for the waves to reflect back from the interface between the coating and the metal pan. The time recorded should reflect whether the coating is at the correct thickness (1.00 mm), which is essential for quality control. To determine the correct reflection time for a 1.00 mm thick coating, we need to consider both the frequency of the ultrasonic transducer, which is 25 kHz, and the wavelength of the ultrasonic waves in the coating, which is given as 0.076 m. The velocity of the sound wave can be calculated from the frequency and wavelength, and subsequently used to calculate the appropriate reflection time for the specified thickness of the coating.