Experiment8.Interference of Ultrasonic Sound Waves OBJECTIVES 1.To observe the interference and diffraction phenomena with ultrasonic sound waves,and uncoverthe law of wave intensity distribution. 2.To observe and study on the ultrasonic beat. 3.To master the principle and the method of Gassy Leb computer measurement and data analysis system. PRINCIPLE The interference and diffraction of coherent(same phase)ultrasonic sound waves,and the principle of ultrasonic sound wave beat are similar to the related phenomena of light. Beats of Ultrasonic Sound Waves Two ultrasonic sound waves of different frequencies interfere with each other and produce the beats of ultrasonic sound waves.Consider two sound waves of same amplitudes and different frequencies, YA=AoSin(2mfat)and YB=AoSin(2ft).Their synthesis wave is exactly Y=2 AoCos〔π(E-fa)t)Sin〔2πt(f+fa)/2) The frequency ofthe synthesis wave is f=f+) The period T of the synthesis wave is called beat period,and corresponding frequency f is called beat frequency. f=1/T Interference of Ultrasonic Sound Waves In this lab,you will use one signal generator to drive two identical ultrasonic transducers to produce two beams of coherent ultrasonic sound waves.The two waves interfere with each other.The result for the angle of maximum intensity ofinterference is sima=n后，n0+12 where n=0,1,2,is referred to as the order of the particular maximum,A is the length of ultrasonic sound wave,and d is the distance between the two ultrasonic transducers. Observation of Ultrasonic Diffraction Place the ultrasonic transducers on the focus of the convex reflector to produce ultrasonic plane wave. Use Gassy Leb computer measurement and data analysis system to observe the phenomena ofsingle, double or multiple silt diffraction(Figure 1).Experiment 8. Interference of Ultrasonic Sound Waves OBJECTIVES 1. To observe the interference and diffraction phenomena with ultrasonic sound waves, and uncover the law of wave intensity distribution. 2. To observe and study on the ultrasonic beat. 3. To master the principle and the method of Gassy Leb computer measurement and data analysissystem. PRINCIPLE The interference and diffraction of coherent (same phase) ultrasonic sound waves, and the principle of ultrasonic sound wave beat are similar to the related phenomena of light. Beats of Ultrasonic Sound Waves Two ultrasonic sound waves of different frequencies interfere with each other and produce the beats of ultrasonic sound waves. Consider two sound waves of same amplitudes and different frequencies, YA=A0Sin(2πfat) and YB=A0Sin(2πfbt). Their synthesis wave is exactly Y = 2A0Cos〔π(fb-fa)t〕Sin〔2πt(fb+fa)/2〕 The frequency of the synthesis wave is f = 1 2 (fa+ fb) The period T of the synthesis wave is called beat period, and corresponding frequency f is called beat frequency. f = 1/T Interference of Ultrasonic Sound Waves In this lab, you will use one signal generator to drive two identical ultrasonic transducers to produce two beams of coherent ultrasonic sound waves. The two waves interfere with each other. The result for the angle of maximum intensity of interference is 𝑠𝑖𝑛 𝛼 = 𝑛 𝛌 𝑑 , n=0,±1,±2… where n = 0, 1, 2, is referred to as the order of the particular maximum, λ is the length of ultrasonic sound wave, and d is the distance between the two ultrasonic transducers. Observation of Ultrasonic Diffraction Place the ultrasonic transducers on the focus of the convex reflector to produce ultrasonic plane wave. Use Gassy Leb computer measurement and data analysis system to observe the phenomena of single， double or multiple silt diffraction(Figure 1)