Electromagnetic Waves & the Electromagnetic Spectrum

Waves… a review Most waves are either longitudinal or transverse. Sound waves are longitudinal. But all electromagnetic waves are transverse…

Electromagnetic Waves Transverse waves without a medium! (They can travel through empty space)

They travel as vibrations in electrical and magnetic fields. Have some magnetic and some electrical properties to them.

Electromagnetic waves travel VERY FAST – around 186,000 miles/sec. (300,000 km/sec.) the speed of light At this speed they can go around the world 8 times in one second.

Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency RADIO WAVES MICROWAVES INFRARED RAYS VISIBLE LIGHT ULTRAVIOLET RAYS X-RAYS GAMMA RAYS

Notice the wavelength is long (Radio waves) and gets shorter (Gamma Rays))

SCIENTIFIC NOTATION A QUICK WAY TO WRITE REALLY BIG OR REALLY, REALLY SMALL NUMBERS.

Rules for Scientific Notation To be in proper scientific notation the number must be written with * a number between 1 and 10 * and multiplied by a power of ten 23 X 10 5 is not in proper scientific notation. Why?

Steps for scientific notation  Place the decimal after the first whole number  Count the number of place values after the decimal (this will be your exponent)  Keep any other non zero numbers  Drop the zeros after the last non zero number

Soooo 137,000,000 can be rewritten as 1.37 X 10 8

Now You Try Using scientific notation, rewrite the following numbers. 347, X ,000, X , X 10 4

Convert these: 1.23 X , X ,806,000

Try These 4,000 4 X X , X ,123, ,000, X 10 8

In the United States, 15,000,000 households use private wells for their water supply. Write this number in scientific notation. 1.5 X 10 7

The U.S. has a total of X 10 7 acres of land reserved for state parks. Write this in standard form. 12,916,000 acres

A number smaller than 0 gives you a negative exponent Follow the same steps, but count to the left of the decimal

Examples Using Scientific Notation, rewrite the following numbers X X X 10 -5

More Examples 1) X ) X ) X ) X ) X 10 -4

The nucleus of a human cell is about 7 X meters in diameter. What is the length in standard notation?

A ribosome, another part of a cell, is about of a meter in diameter. Write the length in scientific notation. 3 X 10 -9

RADIO WAVES Have the longest wavelengths and lowest frequencies of all the electromagnetic waves.

Radio waves Longest wavelength EM waves Uses: TV broadcasting AM and FM broadcast radio Heart rate monitors Cell phone communication MRI (MAGNETIC RESONACE IMAGING) Uses Short wave radio waves with a magnet to create an image

A radio picks up radio waves through an antenna and converts it to sound waves. Each radio station in an area broadcasts at a different frequency. # on radio dial tells frequency.

MRI (MAGNETIC RESONACE IMAGING) Uses Short wave radio waves with a magnet to create an image.

Microwaves Wavelengths from 1 mm- 1 m Uses: Microwave ovens Bluetooth headsets Broadband Wireless Internet Radar GPS

Used in microwave ovens. Waves transfer energy to the water in the food causing them to vibrate which in turn transfers energy in the form of heat to the food.

Global Positioning Systems (GPS) measure the time it takes a radio wave or microwave to travel from several satellites to the receiver, determining the distance to each satellite.

RADAR RADAR (Radio Detection and Ranging) Used to find the speed of an object by sending out EM waves and measuring the time it takes them to return.

INFRARED RAYS Infrared= below red Shorter wavelength and higher frequency than microwaves.

Infrared Radiation Wavelengths in between microwaves and visible light Uses: Night vision goggles Remote controls Heat-seeking missiles

Thermogram—a picture that shows regions of different temperatures in the body. Temperatures are calculated by the amount of infrared radiation given off. people give off infrared rays. Heat lamps give off infrared waves.

VISIBLE LIGHT Shorter wavelength and higher frequency than infrared rays. Electromagnetic waves we can see. Longest wavelength= red light Shortest wavelength= violet (purple) light

The colors we see in objects are the colors that are reflected, all other colors are absorbed. A red t-shirt appears red because red is reflected to our eyes and the other colors are absorbed. When all colors are being reflected we see white light (white isn’t really a color)

When all wavelengths of light are being absorbed we see black (black also, isn’t really a color)

ULTRAVIOLET RAYS Shorter wavelength and higher frequency than visible light Carry more energy than visible light

Ultraviolet Shorter wavelengths than visible light Uses: Black lights Security images on money Harmful to living things Used to sterilize medical equipment Too much causes sun burn Extremely high exposure can cause skin cancer

Used to kill bacteria. (Sterilization of equipment)

Too much can cause skin cancer. Use sun block to protect against (UV rays)

Causes your skin to produce vitamin D (good for teeth and bones)

X-rays Tiny wavelength, high energy waves Uses: Medical imaging Airport security Moderate dose can damaging to cells

X- RAYS Shorter wavelength and higher frequency than UV-rays Carry a great amount of energy Can penetrate most matter.

Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a place where the x- ray was absorbed)

Too much exposure can cause cancer (lead vest at dentist protects organs from unnecessary exposure)

Used by engineers to check for tiny cracks in structures. The rays pass through the cracks and the cracks appear dark on film.

GAMMA RAYS Shorter wavelength and higher frequency than X-rays Carry the greatest amount of energy and penetrate the most.

Gamma Rays  Smallest wavelengths, highest energy EM waves  Uses Sterilizes medical equipment Cancer treatment to kill cancer cells  Kills nearly all living cells.

Used in radiation treatment to kill cancer cells. Can be very harmful if not used correctly.

The Incredible Hulk was the victim of gamma radiation.

Exploding nuclear weapons emit gamma rays.

Brief SUMMARY A. All electromagnetic waves travel at the same speed. (300,000,000 meters/second) in a vacuum. B. They all have different wavelengths and different frequencies. Long wavelength-  lowest frequency Short wavelength  highest frequency The higher the frequency the higher the energy.