Science-Light
The ______ the wave length, the ________ energy it carries
-shorter, more
Umbra?
darkest part of the shadow, no light reaches this
What do all waves transfer?
energy
Do light waves disturb particles?
no
When a fluorescent light is turned on, what happens?
one electrode heats up and releases electrons
What is the order of the electromagnetic spectrum?
radio waves, microwaves, infrared, visible light, ultraviolet, x-ray, gamma rays
Photoluminescence
the atoms take in electromagnetic energy. Which may then be transformed to a kind of electromagnetic energy with less energy. Atoms may emit the light immediately, a process called fluorescence, or over a period of time, in which case the process is called phosphorescence. Examples: (i) the white glow of fluorescent lights, (ii) glow-in-the-dark toys which absorb ultraviolet or visible light and then emit a specific color of light gradually over a period of time.
Bioluminescent
the production of light by chemical reactions in living organisms Example: fireflies and many deep-sea fish
How does it change into visible light?
the uv light collides with the phosphors in the chemical coating on the outside of the tube
What do those electrons do?
they ionize the gas
How are light waves started?
vibrations of particles
whats a solar eclipse?
what happens when the moon gets between the earth and the sun in a position where the earth is in the moons shadow
Whats a lunar eclipse?
when the earth gets between the moon and the sun, so that the shadow of the earth falls on the moon
Can light travel through empty space?
yes
The shorter the wave, the _____________.
more energy it carries
one part of the ________ affects the behavior of the next part of the ___________.
Medium
Neon lights?
-Ex. open sign -these tubes contain neon, krypton, helium, and argon -this glass in the tube becomes ionized, allowing electricity to go through the gas -This causes some electrons in the gas atoms to jump to a higher energy level -the color depends on which gas is in the tube
Tell me about vapor lamps?
-bulbs contain argon, or neon, gas and sodium -when electricity flows to the bulb, it warms up and the sodium changes to vapor which becomes ionized -after a few min., the vapor turns into yellow light -the human eye is sensitive to yellow light, so it seems brighter than other colors
What are three things that could happen when light hits an object?
-light will be reflected -light will be absorbed -light will be transmitted
LED lights
-made of materials called semiconductors -white light is a combination of of different wave lengths -one LED cannot produce white light -red, blue, and green LEDS are combined, because this is how the light appears through human eyes -price is dropping each year -use less electricity than fluorescent bulbs, are very bright
what happens when light is absorbed?
-the electromagnetic energy changes to other kinds of energy
How is intensity defined?
-the energy per unit of area
How is frequency defined?
-the number of vibrations per second
whats an opaque object?
-this does not allow light to pass through it
Why should people use CFL's?
-uses less electricity (75% less than incandescent) -prevent greenhouse gas emissions that cause global warming -contain less mercury than incandescent
Whats a halogen bulb?
Halogen light bulbs are an improvement on the original light bulb design. A halogen bulb also uses a tungsten filament, but it is encased inside a much smaller container made of quartz. Because the container is so close to the filament, it would melt if it were made from glass. The gas inside the container is also different -- it consists of a gas from the group of gases called halogens. These gases have a very interesting characteristic: They combine with tungsten vapor. If the temperature is high enough, the halogen gas will combine with tungsten atoms as they evaporate and redeposit them on the filament. This recycling process lets the filament last a lot longer. In addition, it is now possible to run the filament hotter, meaning you get more visible light per unit of energy. You still get a lot of heat, though; and because the quartz container is so close to the filament, it is extremely hot compared to a normal light bulb.
What is a wavelength?
The distance between the top part of the wave to the top of the next one
Whats a filament of a lightbulb?
The filament in a light bulb is made of a long, incredibly thin length of tungsten metal. In a typical 60-watt bulb, the tungsten filament is about 6.5 feet (2 meters) long but only one-hundredth of an inch thick. The tungsten is arranged in a double coil in order to fit it all in a small space. That is, the filament is wound up to make one coil, and then this coil is wound to make a larger coil. In a 60-watt bulb, the final coil is less than an inch long.
How is amplitude defined?
The maximum displacement from the center of the wave
What happened when the electrons flow through the atoms mercury?
The mercury atoms produce ultraviolet light
Whats the problem with that approach?
The problem with this approach is the evaporation of the tungsten atoms. At such extreme temperatures, some of the tungsten atoms vibrate with enough energy to detach from the atoms around them and go into the air. This is evaporation. As more and more atoms evaporate, the filament starts to disintegrate. The evaporated atoms are carried upwards by convection currents in the gas and are deposited on the glass which starts to get darker. Eventually the filament is too thin and it breaks.
How do waves begin?
With a disturbance
Whats a thin beam of light called?
a ray
Mechanoluminescence
atoms gain energy from mechanical changes such as rubbing the material or deforming it Example: wint-o-green lifesavers produce blue sparks when you bite on them
Electroluminescent
atoms get energy from an electrical current Examples: LEDs and neon lights used in advertising signs
Chemiluminescence
atoms get energy from chemical reactions Example: glow in the dark bracelets which you snap to mix the chemicals and start the reaction.
If the frequency of the wave is ________ it transfers more energy.
higher
What does the speed of the wave describe?
how fast the disturbance is moving through the medium
how could you only see a shadow?
if there is a screen behind it
Explain a fluorescent light bulb.
it consists of sealed glass coated with chemicals called phosphors. The tube is filled with mercury vapor and argon gas at low pressure. At each end of the tube there are electrodes with tungsten filaments.
what happens when an object lets less than 100% of the light pass through?
it creates a shadow!
What does the amplitude of a wave determine?
its intensity
what is an incandescent light source?
light is produced by a hot object
what is an luminescent light source?
light is produced without the need for heating
penumbra?
lighter outer section
