In immersion testing, maximum reflection from the entry surface indicates what?

In immersion testing, maximum reflection from the entry surface typically indicates the optimization of the search unit's alignment with the test material. This optimal alignment facilitates the most efficient transmission of ultrasonic waves into the material, resulting in a strong return signal from the entry surface.

When the search unit is properly normalized, it means that it has been calibrated to work effectively with the characteristics of the material being tested and the medium, in this case, water. A strong reflection not only confirms that the sound waves are passing into the material but also that there are minimal losses or distortions occurring at the entry interface.

In contrast, the other options do not directly relate to the concept of achieving maximum reflection from the entry surface. Eliminating water multiples pertains to mitigating unwanted echoes in the water, while ensuring proper wavelength relates to factors such as frequency and material characteristics, but not directly to surface reflection. The max amplitude of the initial pulse is more about the intensity of the wave being generated rather than the conditions that affect surface reflection in immersion testing.