Nature of Waves

By: Victor R. Oribe

A Vibration is a repeated back and forth motion or oscillation of an object.

Any elastic solid can be made to vibrate.

Amplitude is the maximum displacement an elastic object can make.

When the load is released, it vibrate back and forth.

If the surface is frictionless, then the magnitude of the maximum displacement to the right and to the left of the equilibrium position are equal

The motion of the load repeats itself over and over on a definite path in equal intervals of time.

The periodic vibration of the mass is called Simple Harmonic Motion (SMH).

SMH is a type of vibration along a path in which the displacement of the object from its equilibrium position is always equal above and below its equilibrium position

A simple pendulum oscillates back and forth.

If the pendulum bob moves from A to C then back to A, it has one complete vibration.

The time it takes the pendulum bob to complete one vibration is called the Period or T.

The number of complete vibration in a second is the Frequency or f.

Assignment:1. In your own words, explain the following:

1. vibration2. elastic object3. period4. frequency5. amplitude6. simple harmonic motion7. equilibrium position

2. Explain how waves are produced.

Vibrating objects act as sources of different forms of waves.

Vibrating electrons

Radio waves

Radio waves Earthquake beneath the ocean

Electromagnetic Waves

Waves that need no medium to travel in.

James Clerk Maxwell a Scottish physicist predicted the existence of electromagnetic waves in 1865.

Examples of these waves are: a. light wavesb. radio wavesc. microwavesd. X-rays

Maxwell found out that these waves are produced by oscillating charges.

Mechanical Waves

Waves that need materials medium through which they can travel.

Some examples of mechanical waves are sound waves and water waves, or a waves that travel along a spring or rope.

For the waves in a string, the particles oscillates up and down while the waves move horizontally.

The direction of motion of the particles of the medium (string) is perpendicular to the direction of the waves, these waves are called Transverse Waves.

When the end of the spring is pushed and pulled,

compressions

expansions

a series of compressions and expansions occur.

Compressions and expansions are equivalent to the crest and troughs of a transverse wave.

expansionscompressions

Waves in Different MediaTransverse waves travel through a medium whose particles are attached to one another.

Gas particles are widely separated making transverse waves unable to travel through them.

A longitudinal waves causes particles of a gas to move closer together or farther apart, making gas a medium for it.

Both transverse wave and longitudinal waves can travel through a solid since the particles of solid can vibrate about their relatively fixed positions in any directions.

Guide Questions:1. Differentiate electromagnetic waves from Mechanical waves.

2. What are the different types of mechanical waves?

3. Compare and contrast longitudinal and transverse wave in terms of:

a. direction of oscillation of the particlesb. direction of motion of the wavesc. medium through which they can travel

Wave Characteristics

Crest is the high points on a wave.

Troughs is the low points on wave.

Amplitude is the distance of the crest or trough from the midpoint of the waves.

Wavelength is the distance from crest to crest or trough to trough

Frequency (f) refers to the number of crests or waves that pass a fixed point per second measured in hertz (Hz)

Set workIdentify the different part (characteristics) of waves.

Assignment

1. Give at least five examples on how energy is transmitted by waves.

2. Give at least five reasons how energy is transmitted by waves.

Research Work

1. Make a research on how microwave oven operates.

2. Is it safe to use microwaves oven?

Short Quiz

1. Answer the chapter quiz (Chapter 16).

2. Copy and answer.