nature and sources of light Flashcards
what are the 2 types of light?
natural
artificial
light
the only form of energy that can travel like a wave through empty space and through some materials
what kind of wave does light behave like?
electromagnetic
can you see electromagnetic waves?
no, they are invisible
electromagnetic waves can travel through a ______ at the ______
vacuum / speed of light
what is the speed of light?
3 x 10 to the power of eight m/s
wavelength
distance from the peak of one wave to the peak of the next wave
frequency
number of complete wavelengths that pass a given point in one second
electromagnetic spectrum
diagram that illustrates the arrangement of electronic waves according to wavelength or frequency
low energy= ____ wavelength
long
high energy= ____ wavelength
short
visible light
any electromagnetic wave that the human eye can see
visible spectrum
continuous sequence of different colours together form visible white light
luminous source of light
gives off its own natural light
artificial source of light
production of light by converting external energy forms (chemical, electrical, thermal)
non-luminous source of light
does not give off its own light, may appear bright because of reflection from a luminous object
what are 3 types of light emission?
from the sun
from incandescence
from electric discharge
light from the sun:
fusion reaction: ______ atoms in the sun’s core collide and sometimes ___________
hydrogen / combine or fuse to form
light from the sun:
tremendous amounts of ______ is released
energy
light from the sun:
energy transmitted to the bases on _________
outer layers of sun
light from the sun:
excited atoms release ___________
excess energy
light from the sun:
_____ is emitted
light
light from incandescence
a light emitted by a very hot object
incandescent bulbs are very inefficient at producing light. how much energy used becomes light versus how much energy is lost as heat?
5% light / 95% heat
step one of incandescent lighting
__________ runs through Tungsten wire
electrical current
step two of incandescent lighting
Tungsten wire heats to what temperature?
3000 degrees Celsius
step three of incandescent lighting
____ excites atoms
heat
step four of incandescent lighting
atoms release light– ______ glows
filament
light from incandescence
what is the chemical formula for: chemical energy –> heat + light
CnHn + O2 –> CO2 + H2O + energy
what is energy made up of (in the chemical formula for incandescence)?
heat, light
chemical discharge
electric current passes through a gas or vapour; excites the atom and energy is released; light is emitted
step one of chemical discharge
electron receives _______
energy
step two of chemical discharge
electron gets ______
excited
step three of chemical discharge
light and heat released as _______________
electron loses energy
neon lights– red
neon
neon lights– greenish blue
argon and mercury
neon lights– pale violet
krypton
neon lights– pink
helium
fluorescence
light that is emitted when energy of ultraviolet light is absorbed by a substance and invisible light is converted to visible light
4 benefits to fluorescent bulbs
last longer
use less electrical energy
4x more efficient than incandescent light bulbs
environmentally friendly
2 uses to fluorescent bulbs
forensic investigators can detect fluorescent biological fluids
dentists can detect unhealthy tissue as they appear in darks spots
phosphorescence
light emitted due to exposure of UV light to the source and that continues to be emitted long after the UV light is taken away
chemiluminescence
light that is generated by a chemical reaction without a rise in temperature
bioluminescence
light that is produced by a biochemical reaction in a living organism
wavelengths of light emitted from hot object
short
wavelengths of light emitted from cold object
long
how does a fluorescent bulb work?
energy hits Hg-Ar mixture, invisible UV light is produced and absorbed by fluorescent coating, converted into visible light
luminescence
the emission of light from a substance that has not been heated
which colour has the shortest wavelength?
purple
which colour has the longest wavelength?
red