ELECTROMAGNETIC WAVES

By Mr. Chaiporn Pattanajak

When an electric field changes, so does the magnetic field. The changing magnetic field causes the electric field to change. When one field vibrates—so does the other.• The classification of

electromagnetic waves according to frequency.

Nature of Electromagnetic Waves• They are Transverse waves

without a medium. (They can travel through empty space)

• Energy carrying waves emitted by vibrating charges often electrons that is composed of oscillating electric and magnetic fields that generate one another.

Electromagnetic Waves

• Gamma rays• X-ray• Ultraviolet• Visible light (ROYGBV)

Electromagnetic Waves

• Infrared•Microwave•Radio wave

Electromagnetic Waves

• All EM waves move at the same speed in a vacuum and differ from one another in frequency and wavelenght.

Electromagnetic Waves

• longer wavelength=low frequency=low energy

• Short wavelenght=high frequency=high energy

Electromagnetic Waves

• Gamma rays• X-ray• Ultraviolet• Visible light (ROYGBV)• Infrared• Microwave• Radio wave

Electromagnetic Waves

• The speed of all the waves in the EM spectrum is equivalent to the speed of light 299 792 453 m/s. (300,000,000m/s)

Electromagnetic Waves

• You know more about the electromagnetic spectrum than you may think.

• Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency

• Click here (Animation—Size of EMwaves)RADIO WAVES

MICROWAVES

INFRARED RAYS

VISIBLE LIGHT

ULTRAVIOLET RAYS

X-RAYS

GAMMA RAYS

Waves of the ElectromagneticWaves of the Electromagnetic

Radio WavesRadio Waves

A.Have the longestwavelengths and lowest frequencies of all the electromagnetic waves.

B. A radio picks up radio waves through an antenna and converts it to sound waves.

Radio wave• Your radio captures radio

waves emitted by radio stations, bringing your favorite tunes. Radio waves are also emitted by stars and gases in space.

Radio WavesRadio Waves

Radio waves

• Microwaves—have the shortest wavelengths and the highest frequency of the radio waves.– 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.

– Used by cell phones and pagers.

– RADAR (Radio Detection and Ranging)• Used to find the speed of an object by sending out radio waves

and measuring the time it takes them to return.

MicrowavesMicrowaves

Microwave• Microwave radiation will

cook your popcorn in just a few minutes, but is also used by astronomers to learn about the structure of nearby galaxies.

MicrowavesMicrowaves

Microwaves

• Infrared= below red• Shorter wavelength and higher frequency than

microwaves.• You can feel the longest ones as warmth on your skin• Heat lamps give off infrared waves.• Warm objects give off more heat energy than cool

objects.• Thermogram—a picture that shows regions of

different temperatures in the body. Temperatures are calculated by the amount of infrared radiation given off. Therefore people give off infrared rays.

InfraredInfrared raysrays

Infrared• Night vision goggles pick up

the infrared light emitted by our skin and objects with heat. In space, infrared light helps us map the dust between stars.

Infrared radiationInfrared radiation

Infrared radiation

•Shorter wavelength and higher frequency than infrared rays.

•Electromagnetic waves we can see.•Longest wavelength= red light•Shortest wavelength= violet (purple) light

Visible lightVisible light

Visible Light• Our eyes detect visible light.

Fireflies, light bulbs, and stars all emit visible light.

Visible lightVisible light

Visible light

• Shorter wavelength and higher frequency than visible light

• Carry more energy than visible light• Used to kill bacteria. (Sterilization of

equipment)• Causes your skin to produce vitamin D (good

for teeth and bones)• Used to treat jaundice ( in some new born

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

UltraUltra--violetviolet raysrays

Ultraviolet• Ultraviolet radiation is emitted by

the Sun and are the reason skin tans and burns. "Hot" objects in space emit UV radiation as well.

UltraUltra--violetviolet radiationradiation

Ultra-violet radiation

• 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.

XX--raysrays

X-ray• A dentist uses X-rays to

image your teeth, and airport security uses them to see through your bag. Hot gases in the Universe also emit X-rays.

XX--raysrays

X-rays

•Shorter wavelength and higher frequency than X-rays

•Carry the greatest amount of energyand penetrate the most.

•Used in radiation treatmentto kill cancer cells.

•Can be very harmful if not used correctly.

Gamma raysGamma rays

Gamma ray• Doctors use gamma-ray

imaging to see inside your body. The biggest gamma-ray generator of all is the Universe

Gamma raysGamma rays

Gamma radiation

CREATE A CONCEPT MAP

• Create a concept map about EM waves and speed of light.

3-2-1 EXIT CARD3-What have you learned

today? Explain.2-What life lessons have you

gained from the topic?1-What MI Activity did you

learn the most from?