What is the impact of a lower frequency on ultrasonic testing performance?

A lower frequency in ultrasonic testing leads to an increase in the wavelength of the ultrasonic waves generated. This change in wavelength has practical implications for testing materials.

Longer wavelengths can penetrate through thicker materials more effectively, which is why the statement regarding increased penetration is accurate. The ability to penetrate deeper into materials is essential when dealing with thick components or when inspecting materials with significant attenuation characteristics.

Additionally, as the frequency decreases, the waves are less likely to be scattered by small defects or variations in the material, further enhancing the ability to detect larger flaws that may be present deep within the material structure. Consequently, while lower frequencies improve penetration, they also result in a decrease in resolution. Higher frequencies provide finer details and better resolution in identifying smaller defects.

This is the reason why the correct answer aligns with the understanding that decreased frequency increases wavelength and allows for greater penetration in ultrasonic testing applications.