the question

12 What does the horizontal base line or x-axis on the flaw detector display represent? Time taken for the sound wave to travel through the material b. The distance travelled by the sound wave C. The amplitude of sound energy returning to the probe d. a and b 13 What is another name for the dead zone? a Fresnel zone Fraunhoffer zone Damping Ringing time 14. What is another name for the near zone? a Fresnel zone b . Fraunhoffer zone C. Damping Ringing time 15. What is another name for the far zone? a . Fresnel zone b . Fraunhoffer zone C . Damping d . Ringing time 16. What effect does probe frequency have on crystal ringing time? a. Higher frequency = shorter ringing time b . Higher frequency = longer ringing time C . a and b d. Frequency does not affect ringing time 17. In which zone of the ultrasonic beam do the signal amplitudes become unreliable for comparing defect sizes? a. Far zone b . Fraunhoffer zone C. Dead zone d. Near zone 18. What is the effect on sound beam near zone length, in the same material, when changing to a probe with the same diameter but a lower frequency? a. The length increases b . The length decreases C. a and b d. Probe frequency has no effect on near zone length