Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

Chapter 1: Physical Principles
Q1-10 The acoustic energy reflected at a plexiglass-quartz interface is equal
to?
Answer: R= (Z 1 -Z 2 ) 2 / (Z 1 +Z 2 ) 2 = (3.2-15.2) 2 / (3.2+15.2) 2 = 42.53%
Q1-11 The acoustic energy transmitted through a plexiglass-water interface is
equal to?
Answer: R= (Z 1 -Z 2 ) 2 / (Z 1 +Z 2 ) 2 = (3.2-1.5) 2 / (3.2+1.5) 2 = 13%, T= 1-R = 87%
Q1-12 The first critical angle at a water-plexiglass interface will be?
Answer: ϴ = Sin-1 (1483/2730) = 32.9°