Waves Transverse Longitudinal

Why look at waves? Waves are the key to sound and colour. Mobile phone signals, microwave ovens all use energy carried by waves. Earthquakes and tsunamis are destructive waves of energy.

The ENERGY of the wave moves through matter.

Transverse Waves

Parts of a Wave

Longitudinal Wave (also called Compressional Wave) http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html

Reflection of a Wave From a Boundary

Electromagnetic Spectrum Electromagnetic waves are formed when an electric field (shown as blue arrows) couples with a magnetic field (shown as red arrows).

The magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave.

EM waves arranged by wavelength All types of electromagnetic radiation travel at the speed of light, but differ in wavelength. The electromagnetic spectrum includes gamma rays, X-rays, ultraviolet, visible light, infrared, and radio and microwaves.

Size of WavelengthaInversely Related to Energy of Wave Waves in the electromagnetic spectrum vary in size from very long radio waves the size of buildings, to very short gamma-rays smaller than the size of the nucleus of an atom.

Sound information is encoded within radio waves. CELL PHONES RADIOS TELEVISION

Some objects in space, such as planets and comets, giant clouds of gas and dust, and stars and galaxies, emit long radio waves. VERY LARGE ARRAY In New Mexico RADIO TELESCOPES IMAGE OF CO GASES in our Milky Way

Microwaves Wavelength: 30 cm – 0.3 cm Frequency: Higher than the radio wave’s frequency Energy: Greater than the radio wave’s energy

Microwaves in Radar: Radio detection and ranging The reflected signal will have a "Doppler Shift" proportional to the target speed.

Shorter Microwaves Used for Remote Sensing These microwaves are used for radar like the doppler radar used in weather forecasts. Microwaves, used for radar, are just a few inches long.

Microwaves Microwaves vibrate water molecules to cause friction. The friction produces heat to cook the food.

INFRARED Wavelength: 0.3 cm – 0.0001 cm Frequency: Higher than the microwave’s frequency Energy: Greater than the microwave’s energy

The heat that we feel from sunlight, a fire, a radiator or a warm sidewalk is infrared.

Shorter infrared wavelengths are the ones used by your TV's remote control.

Anything with a temperature emits infrared wavelengths. This image ( which is courtesy of the Infrared Processing and Analysis Center at CalTech), shows a man holding up a lighted match! Which parts of this image do you think have the warmest temperature? How does the temperature of this man's glasses compare to the temperature of his hand?

Visible Light Wavelength: 0.7 micrometer – 0.4 micrometer Frequency: Higher than the infrared’s frequency Energy: Greater than the infrared’s energy

Visible (white) light is made up of all the colors of the rainbow.

Each color has a different wavelength. RED has the longest wavelength. VIOLET has the shortest wavelength.

The leaf only reflects green light Cones in our eyes are receivers for these tiny visible light waves. The Sun is a natural source for visible light waves and our eyes see the reflection of this sunlight off the objects around us. The color of an object that we see is the color of light reflected. All other colors are absorbed.

Ultraviolet Wavelength: 0.4 micrometer – approx. 15 nm Frequency: Higher than the visible light’s frequency Energy: Greater than the visible light’s energy

Positive effects of UV radiation Kills bacteria Prompts the human body to produce Vitamin D

Negative effects of UV radiation Sunburn, wrinkles, premature aging of the skin Skin cancer

X - Rays Wavelength: approx. 14 nm – 0.03 nm Frequency: Higher than the ultraviolet’s frequency Energy: Greater than the ultraviolet’s energy

Bones absorb X-rays When you get an X-ray taken at a hospital, X-ray sensitive film is put on one side of your body, and X-rays are shot through you. At a dentist, the film is put inside your mouth, on one side of your teeth, and X-rays are shot through your jaw, just like in this picture. Because your bones and teeth are dense and absorb more X-rays then your skin does, silhouettes of your bones or teeth are left on the X-ray film while your skin appears transparent. Metal absorbs even more X-rays - can you see the filling in the image of the tooth?

Gamma Rays Wavelength: Smallest wavelength Frequency: Highest frequency Energy: Greatest energy

Gamma rays are not harmful in small amounts These waves are generated by radioactive atoms and in nuclear explosions. Gamma-rays can kill living cells, a fact which medicine uses to its advantage, using gamma-rays to kill cancerous cells.

What is the relationship between frequency and wavelength of the waves in the electromagnetic spectrum?