Electromagnetic Waves

William Gilbert

1544-1603

systematically studied magnetism and coined the term "electricus"

electricus

describe materials that attract small objects

laid the foundation for the study of electricity and magnetism as distinct phenomena

Hans Christian Orsted

1777-1851

he noticed that a magnetic needle moved when an electric current passed through a wire nearby

discovered that an electric current is surrounded by a magnetic field

Michael Faraday

1830s-1850s

discovered that a moving wire through a magnetic field could produce an electric current

Joseph Henry

1797-1878

discovered the phenomenon of electromagnetic induction

induced current

current produced by a magnetic field

James Clerk Maxwell

1831-1879

formulated Maxwell's equation

Maxwell's equation

describe how electric and magnetic fields interact

Heinrich Hertz

1857-1894

proved the existence of radio waves

electromagnetic waves

transverse waves

travels at the speed of light

travels through a vacuum and does not require a medium

propagate through space

transverse waves

oscillations of the electric and magnetic fields are perpendicular to the direction of wave propagation

crest

peak of the transverse wave above the equilibrium position

trough

lowest point of the transverse wave below the equilibrium position

amplitude

maximum displacement of a point from its equilibrium position

measures how far the particles of the medium move from the equilibrium position

larger, more energy

wavelength

λ (m)

distance between two consecutive crests or troughs

length of one complete wave cycle

frequency

f (Hz)

how many complete wave cycles pass a given point per unit of time

inversely related to wavelength

node

point where the wave has zero amplitude

electromagnetic radiation

energy carried by electromagnetic waves

electromagnetic spectrum

range of electromagnetic radiation

higher frequency

shorter wavelength

shorter wavelength

higher energy

radio waves

longest wavelengths and low frequencies

low energy level

non-ionizing radiation

essential for modern communication

non-ionizing radiation

do not have enough energy to ionize atoms or molecules

microwaves

shorter wavelengths and higher frequencies than radio waves

energy is higher than radio waves, lower than infrared

non-ionizing radiation

used to cook and heat food, and communication

infrared

wavelengths longer than visible light, shorter than microwaves

heat radiation

non-ionizing radiation

used in remote controls and thermal cameras

visible light

small portion of the electromagnetic spectrum detectable by the human eye

energy is higher than infrared, lower than ultraviolet

used in photography, photosynthesis, lighting

ultraviolet

shorter wavelengths and higher frequencies than visible light

known for sunburns

used in sterilization, medical, Forensic Science

non-ionizing

x-rays

higher energy and shorter wavelengths than ultraviolet

ionizing radiation

used in x-rays, CT scans

ionizing radiation

enough energy to remove electrons from atoms and molecules, potentially causing significant biological damage

gamma rays

highest energy, high frequency, shortest wavelength

produced by nuclear reactions

ionizing radiation

used in radiation therapy to treat cancer

does not pass through dense materials such as lead or concrete