Waves and Vibrations Introduction PDF

WAVES AND VIBRATIONS WHAT IS A WAVE? A WAVE IS A DISTURBANCE THAT TRAVELS THROUGH A MEDIUM FROM ONE LOCATION TO ANOTHER. A WAVE IS THE MOTION OF A DISTURBANCE 2 I. BASIC INFORMATION A. GENERAL WAVES ARE DEFINED AS A TRANSFER OF ENER...

WAVES AND VIBRATIONS WHAT IS A WAVE? A WAVE IS A DISTURBANCE THAT TRAVELS THROUGH A MEDIUM FROM ONE LOCATION TO ANOTHER. A WAVE IS THE MOTION OF A DISTURBANCE 2 I. BASIC INFORMATION A. GENERAL WAVES ARE DEFINED AS A TRANSFER OF ENERGY BETWEEN TWO POINTS. THE WAVE MAY BE SEEN OR UNSEEN A LIGHT WAVE TRANSFERS ENERGY FROM THE SUN TO THE EARTH A WATER WAVE TRANSFERS ENERGY ACROSS A BODY OF WATER GENERAL DEFINITIONS OF VIBRATIONS AND WAVES A VIBRATION IS ANYTHING THAT SWITCHES BACK AND FORTH, TO AND FRO, SIDE TO SIDE, IN AND OUT, OFF AND ON, LOUD AND SOFT, OR UP AND DOWN. A VIBRATION IS A WIGGLE IN TIME. A WAVE IS A WIGGLE IN BOTH SPACE AND TIME. A WAVE EXTENDS FROM ONE PLACE TO ANOTHER. WAVES ARE PROPAGATIONS OF VIBRATIONS THROUGHOUT SPACE. WAVES TRANSFER ENERGY, NOT MATTER, FROM ONE PLACE TO ANOTHER OSILASI HARMONIK SEDERHANA WAVES ARE EVERYWHERE IN NATURE SOUND WAVES, TELEPHONE CHORD VISIBLE LIGHT WAVES, WAVES, RADIO WAVES, STADIUM WAVES, MICROWAVES, EARTHQUAKE WAVES, WATER WAVES, WAVES ON A STRING, SINE WAVES, SLINKY WAVES 6 Wave from vibration Sound wave Rope wave Sea wave SLINKY WAVE LET’S USE A SLINKY WAVE AS AN EXAMPLE. WHEN THE SLINKY IS STRETCHED FROM END TO END AND IS HELD AT REST, IT ASSUMES A NATURAL POSITION KNOWN AS THE EQUILIBRIUM OR REST POSITION. TO INTRODUCE A WAVE HERE WE MUST FIRST CREATE A DISTURBANCE. WE MUST MOVE A PARTICLE AWAY FROM ITS REST POSITION. 8 SLINKY WAVE ONE WAY TO DO THIS IS TO JERK THE SLINKY FORWARD THE BEGINNING OF THE SLINKY MOVES AWAY FROM ITS EQUILIBRIUM POSITION AND THEN BACK. THE DISTURBANCE CONTINUES DOWN THE SLINKY. THIS DISTURBANCE THAT MOVES DOWN THE SLINKY IS CALLED A PULSE. IF WE KEEP “PULSING” THE SLINKY BACK AND FORTH, WE COULD GET A REPEATING DISTURBANCE. 9  THIS DISTURBANCE WOULD LOOK SOMETHING LIKE THIS THIS TYPE OF WAVE IS CALLED A LONGITUDINAL WAVE. SLINKY THE PULSE IS TRANSFERRED THROUGH THE MEDIUM OF THE WAVE SLINKY, BUT THE SLINKY ITSELF DOES NOT ACTUALLY MOVE. IT JUST DISPLACES FROM ITS REST POSITION AND THEN RETURNS TO IT. SO WHAT REALLY IS10 BEING TRANSFERRED? SLINKY WAVE ENERGY IS BEING TRANSFERRED. THE METAL OF THE SLINKY IS THE MEDIUM IN THAT TRANSFERS THE ENERGY PULSE OF THE WAVE. THE MEDIUM ENDS UP IN THE SAME PLACE AS IT STARTED … IT JUST GETS DISTURBED AND THEN RETURNS TO IT REST POSITION. THE SAME CAN BE SEEN WITH A STADIUM WAVE. 11  LONGITUDINAL WAVE THE WAVE WE SEE HERE IS A LONGITUDINAL WAVE. THE MEDIUM PARTICLES VIBRATE PARALLEL TO THE MOTION OF THE PULSE. THIS IS THE SAME TYPE OF WAVE THAT WE USE TO TRANSFER SOUND. CAN YOU FIGURE OUT HOW?? SHOW TUNING FORK DEMO 12  A second type of wave is a transverse wave. TRANSVERS We said in a longitudinal wave the pulse travels in a direction E WAVES parallel to the disturbance. In a transverse wave the pulse travels perpendicular to the disturbance. 13  TRANSVERSE THE DIFFERENCES BETWEEN THE TWO CAN WAVES BE SEEN 14 CONTINUED THESE DIAGRAMS WILL SHOW WHAT WILL HAPPEN TO AN OBJECT AS A TRANSVERSE WAVE MOVES THROUGH 1. object 2. 3. TRANSVERSE WAVES TRANSVERSE WAVES OCCUR WHEN WE WIGGLE THE SLINKY BACK AND FORTH. THEY ALSO OCCUR WHEN THE SOURCE DISTURBANCE FOLLOWS A PERIODIC MOTION. A SPRING OR A PENDULUM CAN ACCOMPLISH THIS. THE WAVE FORMED HERE IS A SINE WAVE. 16  ANATOMY OF A WAVE NOW WE CAN BEGIN TO DESCRIBE THE ANATOMY OF OUR WAVES. WE WILL USE A TRANSVERSE WAVE TO DESCRIBE THIS SINCE IT IS EASIER TO SEE THE PIECES. 17 ANATOMY OF A WAVE IN OUR WAVE HERE THE DASHED LINE REPRESENTS THE EQUILIBRIUM POSITION. ONCE THE MEDIUM IS DISTURBED, IT MOVES AWAY FROM THIS POSITION AND THEN RETURNS TO IT 18 ANATOMY OF A WAVE crest THE POINTS A AND F ARE CALLED THE CRESTS OF THE WAVE. THIS IS THE POINT WHERE THE WAVE EXHIBITS THE MAXIMUM AMOUNT OF POSITIVE OR UPWARDS DISPLACEMENT 19 ANATOMY OF A WAVE trough THE POINTS D AND I ARE CALLED THE TROUGHS OF THE WAVE. THESE ARE THE POINTS WHERE THE WAVE EXHIBITS ITS MAXIMUM NEGATIVE OR DOWNWARD DISPLACEMENT. 20 ANATOMY OF A WAVE Amplitude THE DISTANCE BETWEEN THE DASHED LINE AND POINT A IS CALLED THE AMPLITUDE OF THE WAVE.\ THIS IS THE MAXIMUM DISPLACEMENT THAT THE WAVE MOVES AWAY FROM ITS EQUILIBRIUM. 21 ANATOMY OF A WAVE wavelength THE DISTANCE BETWEEN TWO CONSECUTIVE SIMILAR POINTS (IN THIS CASE TWO CRESTS) IS CALLED THE WAVELENGTH. THIS IS THE LENGTH OF THE WAVE PULSE. BETWEEN WHAT OTHER POINTS IS CAN A WAVELENGTH BE MEASURED? 22  WHAT ELSE CAN WE DETERMINE? WE KNOW THAT THINGS THAT REPEAT HAVE A FREQUENCY AND A PERIOD. HOW COULD WE FIND A FREQUENCY AND A PERIOD OF A WAVE? ANATOMY OF A WAVE 23  24 WAVE FREQUENCY WE KNOW THAT FREQUENCY MEASURE HOW OFTEN SOMETHING HAPPENS OVER A CERTAIN AMOUNT OF TIME. WE CAN MEASURE HOW MANY TIMES A PULSE PASSES A FIXED POINT OVER A GIVEN AMOUNT OF TIME, AND THIS WILL GIVE US THE FREQUENCY. WAVE FREQUENCY SUPPOSE I WIGGLE A SLINKY BACK AND FORTH, AND COUNT THAT 6 WAVES PASS A POINT IN 2 SECONDS. WHAT WOULD THE FREQUENCY BE? 3 CYCLES / SECOND 3 HZ WE USE THE TERM HERTZ (HZ) TO STAND FOR CYCLES PER SECOND. 25 WAVE PERIOD THE PERIOD DESCRIBES THE SAME THING AS IT DID WITH A PENDULUM. IT IS THE TIME IT TAKES FOR ONE CYCLE TO COMPLETE. IT ALSO IS THE RECIPROCAL OF THE FREQUENCY. T=1/F F=1/T 26  WE CAN USE WHAT WE KNOW TO DETERMINE HOW FAST A WAVE IS MOVING. WHAT IS THE FORMULA FOR VELOCITY? WAVE VELOCITY = DISTANCE / TIME SPEED WHAT DISTANCE DO WE KNOW ABOUT A WAVE WAVELENGTH AND WHAT TIME DO WE KNOW PERIOD 27  SO IF WE PLUG THESE IN WE GET WAVE VELOCITY = LENGTH OF PULSE / SPEED TIME FOR PULSE TO MOVE PASS A FIXED POINT V=/T WE WILL USE THE SYMBOL  TO REPRESENT WAVELENGTH 28 WAVE SPEED V=/T BUT WHAT DOES T EQUAL T=1/F SO WE CAN ALSO WRITE V=F 29 VELOCITY = FREQUENCY * WAVELENGTH THIS IS KNOWN AS THE WAVE EQUATION. WAVE APPLIED ON DEVICE WAVE APPLIED ON DEVICE