Physics: ELECTRO-MAGNETIC WAVE

Electromagnetic waves - produced by a charge that changes its direction or speed.

Electrons are charged particles that can produce electric and magnetic fields

to create the vibrating electric and magnetic fields that are the characteristics of an electromagnetic wave, electrons must move

Charged particle (electron), moves back and forth / vibrate

Changing magnetic field produces magnetic field

electromagnetic wave is made up of an electric field and a magnetic field positioned at right angles to each other and to the direction of motion of the wave

electromagnetic waves are considered as transverse waves, electric and magnetic fields oscillate perpendicular to each other and to the direction of the propagating wave.

Electromagnetic waves travel in a vacuum at a speed of 3x108 m/s and denoted as c, the speed of light. they travel through a vacuum because they do not require matter to exist

Properties of Electromagnetic Waves

1. produced by accelerated or oscillating charge.

2. do not require any material or medium for propagation

3. travel in free space at the speed of 3x108

ELECTROMAGNETIC WAVE THEORY

electromagnetic waves are also produced by a disturbance caused by a vibrating charge

Oersted’s discovery - “A changing electric field produces a magnetic field”

Faraday’s Law - (transverse waves) changing magnetic and electric fields are perpendicular to each other and to their direction of propagation

James Clerk Maxwell - (electromagnetic wave theory) - oscillating electric current should be capable of radiating energy in the form of em waves.

Heinrich Hertz (Hertzian/Radio waves)

Hertz unit used in measuring frequency of waves

Michael Faraday - (electromagnetic induction), contributed to electromagnetic theory of light

Andre-Marie Ampere (wire carrying electric current) can attract or repel to another wire that’s also carrying an electric current

Hans Christian Oersted electric current in a wire can deflect a magnetized compass needle

EM Waves: Frequencies and Wavelengths

electromagnetic spectrum - the order of wavelength and frequency in electromagnetic waves

longest wavelengths have lowest frequencies while shortest wavelengths have highest frequencies (amount of energy carried by an electromagnetic wave increases with its frequency)

1. Radio waves - longest wavelengths, photons w/ lowest energy, football field

2. Microwaves

3. infrared

4. visible light

5. ultraviolet, high ultraviolet

6. x-rays

7. gamma rays - shortest wavelengths, small as the nuclei

   classified as ionizing radiation, photons have enough energy to ionize atoms, causing chem reax

EM waves travel at the speed of light, wavelength and frequency are inversely proportional to each other. Frequencies increase on the EM spectrum, wavelengths decrease.

Waves with longest wavelengths have the lowest frequencies.

Waves with the shortest wavelengths have the highest frequencies.

different types of electromagnetic waves are defined by the amount of energy carried by their photons. Photons are bundles of wave energy.