Increasing the length of the pulse used to activate the search unit will which of the following?

• A. Decrease the penetration of the sound wave
• B. Increase the resolving power of the instrument
• C. Have no effect on the test
• D. Increase the strength of the ultrasound but decrease the resolving power of the instrument

Answer: (D)

Longer pulse length means more cycles are emitted in one shot, delivering more energy into the material. That extra energy makes the echoes you receive stronger, so the ultrasound signal appears more powerful. But the trade-off is that a longer pulse lasts longer in time, which narrows the pulse’s bandwidth. In ultrasonic testing, wider bandwidth (shorter pulses) gives better axial resolution, while a longer pulse reduces this resolving capability. So increasing the pulse length boosts signal strength but lowers the resolving power in the depth direction, matching the option that describes both effects.