Introduction 1

Waves Introduction 1 Next Slide Nature and Properties of Wave • Definition of wave : Disturbances moving from some sources to the surrounding area Photo • Transverse wave and Longitudinal wave Diagram • Examine pulses along a spring (transverse wave)

Waves Introduction 2 Next Slide Basic Terms of Wave • Example (Transverse wave) Diagram • A pulse travelling on a string Diagram • Basic terms to describe a wave : amplitude (A), wavelength (), frequency (f), period (T), wave speed (v) Diagram

Waves Introduction 3 Next Slide Motions in a wave • Motion of particles in a transverse wave Diagram • Graphs we use to describe a transverse wave as well as the motion of particles inside the wave Diagram • Reflection and superposition of pulses in a string Diagram

Waves Stationary Wave 1 Next Slide Stationary wave • Basic arrangement for producing stationary wave : When a long spring is stretched on a smooth floor, with one end fixed and the other end repeatedly flicked sideways, a train of wave is produced. The addition of the incident wave and the reflected wave forms a special wave called a stationary wave. Diagram

Waves Stationary Wave 2 Next Slide Properties of a standing wave • Pattern of a standing wave Diagram • Important differences between a standing wave and a transverse wave Diagram

END of Waves

Waves Introduction 1 Next Slide • Ripples created in a water tank • Paper vibrated by sound

Back to Waves Introduction 1 Click Back to • Particles vibrated by a spring

transverse wave in a spring transverse wave in a string with small beads Waves Introduction 1 Next Slide • Transverse wave

vibration of particles direction of travelling of the wave Waves Introduction 1 Next Slide • Definition of a transverse wave : a wave with the disturbances vibrating at right angles to the direction of travel (direction of energy transmit) of the wave

longitudinal wave in sound longitudinal wave in a string with small beads Waves Introduction 1 Next Slide • Longitudinal wave

vibration of particles direction of travelling of the wave Back to Waves Introduction 1 Click Back to • Definition of a longitudinal wave : a wave with the disturbances vibrating along the direction of travel (direction of energy transmit) of the wave

Back to Waves Introduction 2 Click Back to • A transverse wave is shown below :

Back to Waves Introduction 2 Click Back to • A pulse travelling on a spring :

crest crest trough trough Waves Introduction 2 Next Slide • A transverse wave is shown below :

Waves Introduction 2 Next Slide • Amplitude (A) : the size of the maximum disturbance measured from the resting position (unit : m) • Wavelength () : the minimum distance in which a wave repeats itself (unit : m) • Frequency (f) : the number of complete waves produced in one second (unit : Hz) • Period (T) : the time taken for a particle to make one complete vibration (unit : s) • Wave speed (v) : the speed of propagation of wave (unit : m/s)

 A  direction of travel v (speed)   one complete vibration (different forms) Back to Waves Introduction 2 Click Back to T : time required for one complete vibration f : no. of complete vibrations in one second

B t = 0 s = 0 T E C D A t = 1 s = 1/4 T t = 2 s = 1/2 T t = 3 s = 3/4 T t = 4 s = 1 T Waves Introduction 3 Next Slide

Waves Introduction 3 Next Slide • A transverse wave with : • A = 1 m,  = 2 m, T = 4 sec, f = 1/T = 1/4 Hz (times per sec), v = f = 0.5 m/s • Particles A, D and E are exactly one wavelength apart, they vibrate in phase. These particles have exactly the same motion at any time. • Particles A and C are exactly half a wavelength apart, they vibrate out of phase. These particles have exactly the opposite motion at any time.

Back to Waves Introduction 3 Click Back to • Particle C seems to be trying to catch up with B, but never succeeds. These particles vibrate neither in phase nor out of phase. We say that B leads C or C lags behind B. • Motion of particle A : i. When t = 1 s (1/4 T), particle A is momentarily at rest. ii. When t = 2 s (1/2 T), particle A is moving up. iii. When t = 3 s (3/4 T), particle A is momentarily at rest. iv. When t = 4 s (1 T), particle A is moving down.

B A direction of travel Waves Introduction 3 Next Slide • A transverse wave is shown below :

displacement 0 distance Waves Introduction 3 Next Slide • Displacement of particles vs distance graph of the wave at a certain time : • The graph shows the displacements of the particles at different positions in the wave. The shape of the graph is the same as that of the wave itself.

displacement A 0 time B Back to Waves Introduction 3 Click Back to • Displacement vs time graphs of particle A and particle B in the wave : • The graph shows the motion of a particle in the wave. It’s shape varies for different particles.

incident pulse reflected pulse incident pulse reflected pulse Waves Introduction 3 Next Slide • A pulse travelling on a string with a fixed end. • A pulse travelling on a string with a free end.

Waves Introduction 3 Next Slide • The pulse travels with a constant speed along the spring and its amplitude decreases gradually. • The pulse speed increases when the spring is stretched more. • The pulse is reflected at the fixed end, and the reflected pulse is always opposite to the incident pulse.

Back to Waves Introduction 3 Click Back to • The superposition of the two pulses is shown below :

  long spring incident wave reflected wave Waves Stationary Wave 1 Next Slide • The superposition of the incident wave and reflected wave on a long spring is shown :

A N A N A N A N A N A N A N A N  A : Anti-node ( points with maximum amplitude) N : Node (points with zero amplitude) Back to Waves Stationary Wave 1 Click Back to • At last, the pattern of the string will become : • distance between successive nodes or anti-nodes is equal to /2

t = 0 T t = 1/2 T t = 1/8 T t = 5/8 T t = 1/4 T t = 3/4 T t = 3/8 T t = 7/8 T Back to Waves Stationary Wave 2 Click Back to

Stationary Wave Travelling Wave does not move to any direction moves to a direction (v  0) amplitude is not the same for all particles amplitude is the same for all particles energy is stored inside the wave at certain positions energy is transmitted to other places through the wave Back to Waves Stationary Wave 2 Click Back to

Introduction 1

Introduction 1

Presentation Transcript

1. Introduction

1. INTRODUCTION

1. Introduction

1. INTRODUCTION

1 Introduction

CH.1 Introduction 1-1 Introduction

1. Introduction

1-1 Introduction

1. INTRODUCTION

1. Introduction

1. Introduction

1. Introduction

Introduction 1

1: Introduction

INTRODUCTION (1)

1: Introduction

1. Introduction

1 INTRODUCTION