WavesWe live in a world of waves- from the simple water waves generated when we throw a coin in a wishing well,

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the music as we strum a guitar,

the thunder associated with a storm to the dangerous tsunami and earthquakes.

To see the unborn

Wave- a disturbance traveling through a medium or in vacuum.

Wave Pulse - A single unrepeated disturbance Wave Train- A succession of periodic disturbances

CLASSIFICATION OF WAVES1.Nature: A. Mechanical waves -require a material medium to propagate. B. Electromagnetic waves -can travel in vacuum and in material media.

2. Direction of Propagation A. Transverse waves

B. Longitudinal Waves

Transverse wave - particles of the medium are vibrating perpendicularly to the direction of wave propagation. - made up of alternating hills and valleys. The top of the hill is called crest while the bottom of the valley is called trough. - Crest is the position of maximum upward displacement from equilibrium position. -Trough is the position of maximum downward displacement from equilibrium position.

Transverse Wave

B. Longitudinal Wavesparticles of the medium vibrate parallel to the direction of wave propagation. composed of compressions and rarefactionsCompressions are where particles of medium are closer together.Rarefactions where they are farther apart. Compression corresponds to crest in transverse waves and rarefaction to trough. Sound waves are longitudinal waves.

LONGITUDINAL WAVES

Some waves have both longitudinal and transverse properties. Seismic waves or waves generated by an earthquake or explosion are classified into two: body waves and surface waves.

Body waves travel through the earths interior and are divided into primary wave or P wave and secondary or S wave. P waves are longitudinal while S waves are transverse.

Surface waves, as the name suggests travel at the surface.

Surface waves are further classified into Love waves and Rayleigh waves.

Love waves were named after A.E. H. Love and were the fastest surface wave. Rayleigh wave, named after Lord Rayleigh.

Rayleigh WavesParticles of medium move in elliptical pathsParticles at the surface move in counterclockwise ellipseParticles at a depth of 1/5 wavelength move in clockwise ellipses. are responsible for the shaking felt during an earthquake.

( Dr. Dan Russell, Kettering University)

Rayleigh Wave

Water WavesEach particle in the surface of water moves in circular orbits.

Electromagnetic WavesElectromagnetic waves are produced by oscillating electric charges with the electric field and magnetic field vibrating perpendicularly with each other and to the direction of wave propagation.

The electric field and magnetic field of an electromagnetic wave are perpendicular to each other and to the direction of motion of wave. E stands for electric field, B stands for magnetic field and c for the velocity of electromagnetic wave.

They all propagate through vacuum (or air) with the same speed equal to 3 x108m/s

In 1862, James Clerk Maxwell predicted the existence of electromagnetic waves. However, it was until 1887 through the efforts of Heinrich Hertz when those waves (except light) were observed to exist.

Electromagnetic Spectrum

Electromagnetic spectrum is a term used to describe the entire range of electromagnetic radiations arranged in the order of their frequencies or wavelengths.

Radio WavesRadio waves are the longest of all electromagnetic waves, ranging from 10-1m to 104m. They were discovered by Heinrich Hertz in 1887. They are produced by electronic devices like LC oscillators. The sun and the planet Jupiter are extraterrestrial sources of radio waves.

They are divided into a) long waves b) medium waves used by AM stations c) VHF (very high frequency) used by FM stations d) ULF (ultra high frequency) used by police radio communications military aircraft and television transmissions.

UsesRF IDs- soon to replace the barcode in most grocery items.

The EC tag that we use to pay tolls in South Luzon Expressway and North Luzon Expressway is another form of RFID.

MRI Scan

Fractal Antenna

Wireless CommunicationBluetooth a cable replacement technology founded in 1998by Ericcson, Nokia, Intel, Toshiba and IBM. small radio chip inserted into computers, printers, cell phone that carries information and transmits it to a receiver at frequency 2.45Ghz

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The Bluetooth Logo unites the Runic alphabetic characters "H", which looks similar to an asterisk, and a "B", which are the initials for Harald Bltand.

WiFi is a wireless technology that provides easy and fast Internet access

WiMax is an acronym for Worldwide Interoperability for Microwave Access

MicrowavesMicrowaves are extremely high frequency radio waves. James Clerk Maxwell was credited for discovering microwaves in 1864. They have short wave lengths: from 10-4m to 10-1m and very easily absorbed by water molecules. That is why they are used in microwave ovens.

Microwave Antenna Farm inNCU, Taiwan

Microwave Antenna at Remote sensing Lab, NCU

Infrared WavesInfrared rays have longer wavelengths than red. Their wavelengths range from 7 x 10-7m - 10-3m. Sir William Herschel identified these rays about 1800. Infrared rays are also known as heat waves. The danger of too much exposure to infrared rays will lead to overheating (but of course!).

Infrared rays are used in remote controls for televisions, burglar alarm systems and night visions.

Physiotherapists use heat lamp to heal sports injury.

Uses

Visible LightLight is the part of the electromagnetic spectrum visible to our unaided eye.

It extends from the short wave violet ( = 4 x 10-7m) to the long wave red ( =7.6 x 10-7m).

Ultraviolet RaysJohann Wilhelm Ritter discovered the ultraviolet rays (UV for short). UV rays have wavelengths ranging from 6x 10-10m to 4 x 10-7m.

A major source of ultra violet rays is the sun.

Special lamps also emit UV rays. UV rays are used to detect forged bank notes. UV rays also make visible the security marker ink that we use for our signatures in our bankbook. It is also a good source of vitamin D. It is a common practice to expose babies to sunlight in the morning for their bones to get stronger.

UV rays are also used to sterilize medical equipments.

too much exposure to ultraviolet rays burns our skin and produces the so -called sun tan.

UV rays can also cause skin cancer.

Ultraviolet rays can also damage the retina.

Theaters

X-RaysX-rays or Roentgen rays are thousand times shorter than the shortest visible light and have very high frequencies.

X- rays have wavelengths ranging from 10-12m to 10-8m.

To photograph our internal body parts, airport security checks to see the inside of your luggage.

X rays can cause cancer and damage tissues.

WILHELM CONRAD ROENTGEN

As a young boy, he was drawn to nature and loved to experiment. His schooldays were quite troublesome. He was even expelled from Utrecht Technical School for making a caricature of one of his teachers, a crime he did not admit. He was often quoted saying A man must have luck in life to get anywhere. Truly enough, this man must be very lucky for having accidentally discovered X-rays while working on cathode ray tubes. For this discovery, he was awarded the very first Nobel Prize in Physics in 1901

Do you know thatOne of the first X-ray photograph that Roentgen produced was that of his wife hand. Note the wedding ring in her finger.

Gamma RaysGamma rays are given off by radioactive materials like Cobalt 60 and Cesium 137. Gamma rays are highly penetrating because of their very short wavelengths ranging from less than 10-14m to 10-10m.

Gamma rays are used in industries to detect cracks in metals.

They can cause cancer and even mutation. But the irony of it, gamma rays are used to destroy cancer cells Paul Villard was given the credit for discovering gamma rays in 1900.

Wave Terminology1. The period (T) of a vibratory motion is the time required to make a complete to and fro motion. One to and fro motion is called a cycle. Period is usually expressed in seconds.

Frequency (f) is the number of cycles per unit time. Its SI unit is the hertz, abbreviated as Hz. 1 Hz = 1 cycle/second. Frequency is the reciprocal of period.

Amplitude (A) of vibration - the maximum displacement of the body from its equilibrium position.

Wavelength is the distance between any two successive points in a wave that are in phase with each other.

Two points are in phase with each other if they have the same mode of vibration. Otherwise, they are out of phase.

Basic Wave Equation

V= f where v is the velocity of the wave in meters/second, f is the frequency in Hertz and is the wavelength in meters.

ExampleOn your radio, you have an AM band and an FM band. AM means amplitude modulation and FM means frequency modulation. Suppose a station broadcasts on two radio frequencies: 630kHz and 101.9MHz on your radio dial. Find the wavelength for each frequency.

Example 2A transverse wave on a rope is shown below. What is the a) wavelength b) amplitude c) If the frequency of the wave is 5Hz, what is its velocity?

WATER WAVESWater waves are classified as deepwater waves or shallow water waves. If the depth of the water is much greater than , the waves are deepwater waves.

Deepwater waves are short waves. Each particle in the surface of water moves in circular orbits.

. Shallow water waves are long waves propagating with a velocity given by the following equation

where h is the depth of water and g is the acceleration due to gravity.

While fishing, you notice that 8 crests pass a given point in a time interval of 10s. You approximate the distance between 2 crests to be 1.2m. Calculate the a) speed of water waves and b) depth of water.

Wave PropertiesReflection the turning back of a wave to the original direction it is traveling upon hitting an object.

Refraction the change in direction and change in wavelength or velocity of the wave that occurs as the wave is transmitted from one medium to another.

DiffractionWaves bend around obstacles in their path or spread out when they travel through narrow slits.Charactertized by bright and dark fringes

Activity: look through your finger

Diffraction through narrow and wide opening

Diffraction bright and dark bands

Doppler EffectApparent change in frequency due to relative motion between source and observer.

Wala ng wangwang!

DOPPLER EFFECT FOR LIGHT:UNIVERSE IS EXPANDING!Light emitted by a star is redshifted! The star must be moving away from us!

Energy Transmission of Wave

ResonanceAll objects have a tendency to vibrate at a characteristic frequency called its natural frequency. Resonance is said to occur when an object vibrates at its natural frequency upon receiving impulses from a source vibrating at the natural frequency of the object. The result of resonance is a wave of greatly increased amplitude on the part of the object.

Collapse of Tacoma Narrows Bridge

A revolving antenna sends out signals consisting of pulses of radio waves or microwaves. These waves bounce off falling rain, snow or hail and return to the antenna. From the change in the frequency of the signal, the velocity as well as direction of rain may be determined. Distance and intensity of rainfall may be estimated from the time the reflected signals return to the antenna. A computer software interprets the data and produce the kind of weather map we see on television. *