Physics: Light as Electromagnetic Wave

Light as a Wave
 ______ is a visible form of energy
 most of the energy that surrounds us is __________
 this energy travels in ______ made of electric and magnetic fields
 called “________”
 ______________ = the entire range of visible and invisible energy waves

Electromagnetic Wave
 Electromagnetic waves are Wave Transverse waves without a ________ (They can travel through empty space)
 They travel as _________ in electrical and magnetic fields.
- Have some magnetic and some electrical properties to them.

 Electromagnetic waves travel VERY FAST-around _____________ (the
speed of light).
 At this speed they can go around the world _ times in one second.

Waves or Particles?
 Electromagnetic radiation has properties of _____ but also can be thought of as a stream of _________.
Example: Light
 Light as a wave: Light behaves as a ________ which we can filter
using polarized lenses.
 Light as particles (photons): When directed at a substance light can knock
electrons off of a substance (__________)

name for the range of electromagnetic waves when placed in order of increasing frequency

 Longer than radio, shorter than infrared or visible light
 Wavelength 1 x 10-4 m to 1 x10-1 m

 used for communication, medicine and consumer use (microwave ovens)

 ___________ Have the longest wavelengths and lowest frequencies of all the electromagnetic waves.
 Low energy waves with long wavelengths
 Includes FM, AM, radar and TV waves Wavelengths of 10’‘m and longer
 Low frequency
 Used in many devices such as remote control items, cell phones, wireless devices, etc.

______________ measure the time it takes a radio wave to travel
from several satellites to the receiver, determining the distance to each satellite,
A radio picks up radio waves through an antenna and converts it to sound waves.
 Each radio station in an area broadcasts at a different frequency.

 _____________ Uses Short wave radio waves with a magnet to create an image.
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 to find the speed of an object by sending out radio waves and measuring the time it takes them to return.

Infrared Rays
 _______ = below red Shorter wavelength and higher frequency than microwaves.
 ________ -a picture that shows regions of different temperatures in the body.

Temperatures are calculated by the amount of _________ radiation given off.
 Therefore people give off infrared rays.
 Heat lamps give off infrared waves.

 Shorter wavelength and higher frequency than infrared rays.
 Electromagnetic waves we can see.
 Longest wavelength= _________
 Shortest wavelength= ___________
 When light enters a new medium it ________. Each wavelength bends a different
amount allowing white light to separate into it’s various colors ROYGBIV

 Higher energy than light waves
 Can cause skin cancer and blindness in humans
 Used in tanning beds and sterilizing equipment
Ultraviolet Rays
 Shorter wavelength and higher frequency than visible light
 Carry more energy than visible light
 Used to kill bacteria. (Sterilization of equipment)
 Too much can cause skin cancer. Use sun block to protect against (UV rays)
 Causes your skin to produce vitamin D (good for teeth and bones)

 High energy waves
 Used in medicine, industry and astronomy
 Can cause cancer
 Shorter wavelength and higher frequency than UV-rays
 Carry a great amount of energy
 Can penetrate most matter.
 Examples:
 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

 Highest energy
 Blocked from Earth’s surface by atmosphere
 Shorter wavelength and higher frequency than X-rays
 Carry the greatest amount of energy and penetrate the most.
 Examples:
 Used in radiation treatment to kill cancer cells
 Can be very harmful if not used correctly.
 The Incredible Hulk was the victim of gamma radiation.
 Exploding nuclear weapons emit gamma rays.

Brief Summary
 All electromagnetic waves travel at the _______ speed.
 (____________ meters/second) in a vacuum.
 They all have different wavelengths and different frequencies
 Long wavelength - ________
 Short wavelength - ________
 The higher the frequency the ________

How Light is Transmitted

 ________: allows light to pass through
________: allows some light to pass through
 __________: allows no light to pass through

Light Reflection
 The reason we see objects is because they __________