REVIEW FOR ALL WAVESELECTROMAGNETIC WAVES All Waves are caused by a vibration. Every vibration has a frequency, f, and a period, T. The frequency of any wave is the number of times it vibrates in one second (hz). Electromagnetic waves are caused by a vibrating electric charge (usually an electron). Every electromagnetic wave has a frequency, f, and a period, T. The frequency of an electromagnetic wave is the number of times the electric charge vibrates in one second (hz).
REVIEW FOR ALL WAVESELECTROMAGNETIC WAVES The matter that waves travel through is called the medium. Some waves, called mechanical waves, require a medium to travel. Other waves don’t. Sound is an example of a mechanical wave. Sound travels by vibrating the matter it is travelling through (its medium). Sound cannot travel through a vacuum. Electromagnetic waves can travel through a medium. Electromagnetic waves do not require a medium to travel. Light is an example of an electromagnetic wave. Light can travel through a vacuum (no matter).
REVIEW FOR SOUNDELECTROMAGNETIC WAVES Sound is a longitudinal wave. This means the vibration that produces the sound travels along the same direction as the wave moves. Electromagnetic (EM) waves are transverse waves. This means the vibration that produces the EM wave travels perpendicular to the direction the wave travels. Direction of Travel Vibration
The wavelength, λ, is the distance between the peaks (crests) of an electromagnetic wave. The amplitude, A, is the maximum displacement from the equilibrium position for an electromagnetic wave. Equilibrium Position wavelength, λ Amplitude, A
REVIEW FOR SOUNDELECTROMAGNETIC WAVES Sound travels at a constant speed in the same medium. This constant speed is called the speed of sound. In air (20 o C @ sea level) the speed of sound is 340-m/s or 760-mph. Electromagnetic (EM) waves travel at a constant speed in the same medium. This constant speed is called the speed of light, c. The speed of light in a vacuum is 3 X 10 8 -m/s (300,000,000-m/s) or 186,000-mi/sec. NOTHING travels faster than the speed of light!!!!