Warm Up
1. What is energy?2. What is kinetic energy? How do you
calculate it?3. What is potential energy?4. What is a transverse wave? Draw and
label. 5. What is a longitudinal wave? Draw and
label.
I. Electromagnetic Waves
Waves… a review
Most waves are either longitudinal or transverse.
Sound waves are longitudinal.But *all electromagnetic waves are
transverse…
?
?
1. When an electric field changes, so does the magnetic field. When one field vibrates—so does the other.
2. RESULT- An electromagnetic
wave.
Click here Animation: Interaction of vibrating charges
A. Electromagnetic waves1. Produced by the movement of electrically
charged particles. They are transverse waves
2. Can travel in a “vacuum” (they do NOT need a medium)
3. Travel at the speed of
light: 300,000,000 meters/second (Takes light 8 minutes to move from
the sun to earth {150 million miles}
at this speed.)
(Also known as EM waves)
Waves of the Electromagnetic SpectrumElectromagnetic 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
Wave-particle Duality
Light can behave like a wave or like a particle
A “particle” of light is called a photon
Radio wavesHave the longest wavelengths and
lowest frequencies of all the electromagnetic waves.
Uses:TV broadcastingAM and FM broadcast radio ( each channel is
a different frequency)Cell phone communication
MicrowavesMicrowaves—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.
How does a microwave oven work?
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.)
Infrared RadiationWavelengths in between microwaves and
visible light Infrared means Before RedUses:
Night vision gogglesRemote controlsHeat-seeking missiles
Visible light
Only type of EM wave able to be detected by the human eye
Violet is the highest frequency lightRed light is the lowest frequency light
Ultraviolet
Shorter wavelengths than visible lightUses:
Black lightsSterilizing medical equipmentWater disinfectionSecurity images on money
Ultraviolet (cont.)
UVA UVB and UVC
Energy Highest of UV waves
Lower than UVA
Health risks
Extremely low risk for DNA damage Can destroy Vitamin A in skin
Can cause DNA damage, leading to skin cancer Responsible for sunburn
X-rays
Tiny wavelength, high
energy wavesUses:
Medical imagingAirport securityInspecting industrial welds
Gamma Rays
Smallest wavelengths, highest energy EM waves
UsesFood irradiationCancer treatmentTreating wood flooring
Using the EM waves to view the Sun
Animation—View a Galaxy at different wavelengths
Brief SUMMARYA. All electromagnetic waves travel at the
same speed. (300,000,000 meters/second in a vacuum.
B. They all have different wavelength and different frequencies.Long wavelength-lowest frequencyShort wavelength highest frequencyThe higher the frequency the higher the
energy.