prelab4

# prelab4 - 12. PRELAB FOR INTERFERENCE LAB 1. INTRODUCTION...

This preview shows pages 1–2. Sign up to view the full content.

12: Interference Lab - 1 12. PRELAB FOR INTERFERENCE LAB 1. INTRODUCTION As you have seen in your studies of standing waves, a wave and its reflection can add together “ constructively ” (peak meets peak, giving large amplitude) or destructively ” (peak meets valley, canceling each other). This type of adding is called INTERFERENCE , and it depends on the relative phase of the interfering waves. Since the direct and reflected waves are coming from the same source, they clearly start out in phase . Whether or not they come back together in phase depends on path length. If the difference in the two path lengths is 1,2,3,etc. wavelengths , then the waves will be back in phase. If there is an extra ½ wavelength, however, they will be out of phase. 2. AN EXAMPLE OF MICROPHONE PLACEMENT The next page contains an excerpt from an article on the importance of a microphone placement. Read the excerpt and answer the following questions: 1. When the pressure wave is reflected from the table, is there a 180 o phase shift? (Think back to the standing waves in the open and closed tubes). 2. Look at Fig. 4.10 from the excerpt. Suppose that the direct sound travels 2 meters, and the reflected sound covers a greater distance of 2 ½ meters. Therefore, the difference in the two path lengths is d = 0.5m. Constructive interference will occur when d = λ , 2 λ , 3 λ , 4 λ , … , where λ is the wavelength. Use the relation v = λ f , (v – speed of sound, f – frequency) to calculate the first four frequencies at which constructive interference will occur. Assume v = 344 m/s. Then, calculate the first four frequencies at which destructive interference ( d = ½ λ , (1+ ½) λ , (2+ ½) λ , …) will occur.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 01/20/2012 for the course P 109 taught by Professor Staff during the Fall '08 term at Indiana.

### Page1 / 8

prelab4 - 12. PRELAB FOR INTERFERENCE LAB 1. INTRODUCTION...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online