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Level 182

Nature of Light


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Electromagnetic Spectrum
a group of different types of waves (radio waves, microwaves, infrared waves, visible light, ultraviolet light, x-rays, gamma rays)
radio waves
electromagnetic waves with the longest wavelength and lowest frequencies
radar
a system that uses reflected waves to detect objects and measure their distance and speed
microwaves
electromagnetic waves that can cause water molecules inside food to vibrate, heating the food.
infrared (IR)
electromagnetic waves that have wavelengths slightly longer than wavelengths of red visible light
ultraviolet
higher energy and shorter wavelengths than visible light; makes up 9% of energy emitted by the sun They are the reason we wear sunscreen.
x-rays
electromagnetic waves used to make images of bones and teeth
gamma rays
electromagnetic waves with the shortest wavelength and the highest frequencies
vitamin D
Skin cells produce this when exposed to ultraviolet light.
Energy
(physics) the capacity of a physical system to do work
wavelength and frequency
Electromagnetic waves are classified in a spectrum according to these two properties of waves.
Transverse waves
Electromagnetic waves are
tanning booth
A device that uses ultraviolet (UV) light.
cell phone
A device that uses microwaves.
visible light
electromagnetic waves that can be seen with the unaided eye
night vision goggles
A device which uses infrared (IR) waves to allow you to see at night
light
Refraction is caused by changes in the speed of _______ as it passes from one material to another.
particles and waves
light has properties of both _______ and _______
light as a wave
Fluctuating electric and magnetic field
186,000 miles per second
speed of light particle as it radiates from its source in a wave pattern
visible spectrum
the part of the electromagnetic spectrum that can be seen. visible ligth makes up only 35 percent of natural sunlight
Light Sources
the sun; incandescence; electrical discharge; fluorescence; luminescence
Incandescence
A process that makes light with heat
Gas Discharge
process of producing light by passing an electrical charge through a gas e.g. sodium lamps
Photoluminescence
the emission of light from a substance that has absorbed light energy
Phosphors
substances that emit visible light when struck by radiation e.g. cathode ray tubes on a t.v.
Color Temperature
the warmth or coolness of a color. eg blue is cool and orange is warm
Photometry
The art of measuring the intensity of light.
Transparent
All light passes through; can see through clearly eg. glass
translucent
a type of material that scatters light as it passes through it
opaque
impossible to see through; preventing the passage of light
transmission of light
When a light wave passes through an object however Some alteration of the light wave does take place, e.g. change direction, slowing down, refracted
refraction
a wave is bent due to a change in speed
scattering
reflection of light in all directions
absorption
(physics) the process in which incident radiated energy is retained without reflection or transmission on passing through a medium
Photoreceptors
Cells inside the retina
perception variables
psychological/emotional, physiological, and environmental
emotional variable
e.g red is regarded as a hot color and is seen to provoke anger or aggression, black is associated with death, dignity, white with purity, and green with fertility
physiological variable
color blindness due to some deficiency in color sensitive pigments in the cones of your eyes
primary colors
Pure or fundamental colors (red, yellow, and blue) that cannot be created by combining other colors.
secondary colors
Colors obtained by mixing equal parts of two primary colors, Green, Orange, Violet
additive primary colors
Red, blue, and green light. These colors when added together produce white light.
subtractive primary colors
The colors of magenta, yellow, and cyan- that, when mixed in certain proportions, reflect any other color in the visible-light part of the electromagnetic spectrum
infrared
it is the radiation that heat gives off
cone cells
function in color vision and visual acuity
rod cells
work best in dim light and enable you to see black, white, and shades of gray
flouresence
photons kick an electron to an outer valence, if its not picked off, it falls back releasing a photon of energy (always red)
Electromagnetic waves🎀
Waves that do not require a medium, but can travel through a medium (light from the sun is a type of electromagnetic)
Radiation🎀
The transfer of energy through matter or space as electromagnetic waves, such as visible light and infrared waves
Speed of light🎀
186,000 miles per second, or about 671 million miles per hour
Electromagnetic spectrum🎀
The entire range of electromagnetic waves
Field🎀
A region around an object that can exert a force, a push or pull on another object
electromagnetic wave
a transverse wave that involves the transfer of electric and magnetic energy
Radio receiver🎀
A radio receives radio waves and then converts them into an electric current, which is then converted into sound
Modulation🎀
Changing amplitude or frequency of radio waves; AM for amplitude modulation or FM for frequency modulation
AM🎀
Am Radio waves can reflect of the ionosphere. This helps AM waves travel long distances
FM🎀
FM radio waves pass through the ionosphere. Therefore, FM waves cannot travel as far as AM waves.
Microwaves🎀
Have shorter wavelengths and higher frequencies than radio waves; carry more energy than radio waves
Radar🎀
Microwaves are used in radar; used to detect the speed and location of objects; short pulses of microwaves are emitted and Boyce off the car and return to the source.
Infrared waves🎀
Infrared have shorter wavelengths and higher frequencies than microwaves; warm objects give off infrared radiation.
Visible light🎀
The very narrow range of wavelengths and frequencies in the electromagnetic spectrum that humans can see
Visible spectrum🎀
The range of colors that you can see in a rainbow.
Ultraviolet light🎀
Has shorter wavelengths and higher frequencies than visible light; overexposure can cause skin damage.
X-rays🎀
Have some of the shortest wavelengths and highest frequencies of all EM waves; carry a great deal of energy and penetrate a variety of materials which is very useful in the medical field
Gamma rays🎀
Have some of the shortest wavelengths and highest frequencies of all EM waves; carry large amounts of energy which make them useful as artist ion treatments for cancer.
Reflection🎀
Occurs when light or any other wave bounces off an object.
Law of reflection🎀
States that the angle of incidence is equal to the angle of reflection.
Incidence🎀
The beam of light traveling toward the reflecting surface.
Specular reflection🎀
Reflection off a very smooth surface when all reflected beams are at the same angle
Diffuse reflection🎀
Reflection off a rough surface and the reflected beams are of many different angles
Absorption🎀
The transfer of energy carried by light waves to particles of matter
Scattering🎀
The release of light energy by particles of matter that have absorbed energy; light with shorter wavelengths, such as blue, scatter the most (is what makes the sky blue)
Diffraction🎀
The bending of waves around a barrier or through an opening
Interference🎀
A wave interaction that occurs when two or more waves overlap.
Constructive interference🎀
When waves combine and the resulting wave has a greater amplitude the individual waves had
Destructive interference🎀
When waves combine and the resulting wave has a smaller amplitude than the individual waves had; results in dinner light
Transmission 🎀
the passing of light through matter; includes transparent translucent, but not opaque
Transparent🎀
Matter through which visibleivht is easily transmitted; includes air, clear glass, and water
Translucent🎀
Matter transmits light but also scatters the light as it passes through the matter; includes wax paper and frosted glass
Opaque🎀
Matter that does not transmit any light
Pigment🎀
A material that gives a substance it's color by absorbing some colors of light and reflecting others
Primary colors of light🎀
Red, blue, and green are the _?_ colors of light
Secondary colors of light🎀
When two primary colors are added together, a _?_ color is produced; include yellow, magenta, and cyan
Radio waves🎀
All radio and television stations broadcast radio waves; have some of the longest wavelengths and lowest frequencies of all EM waves