A larger diameter crystal results in less beam spread

• A. Beam spread increases
• B. Less beam spread
• C. No effect on beam spread
• D. Beam width becomes narrower with more material

Answer: (B)

A larger diameter crystal acts as a bigger aperture, which reduces diffraction and makes the ultrasonic beam more directional. In simple terms, the divergence angle is tied to the wavelength divided by the aperture size; increasing the diameter lowers this angle, so the beam spreads less as it travels. That’s why the correct description is less beam spread. The idea that beam spread would increase, have no effect, or that beam width simply becomes narrower because of more material doesn’t align with how diffraction from the transducer aperture works.