physics quiz 1 (3.1-3.8) Flashcards
define incandescence light
- light is produced as result of high temperature
- electrical energy passes from socket—>metal (filament) which turns into heat energy and is released as light
- not energy efficient
initial source of energy of incandescent light
electrical energy
define electrical discharge
- light is produced by passing electric current through gas
- electricity makes the gas glow
- as atoms gain and lose energy, light energy is released
initial source of electric discharge
electrical energy
define phosphorescence
- light produced by UV light absorption which emits over time (ex. glow in the dark items)
- non-luminous objects that become luminous near luminous sources
- light from luminous source is absorbed by phosphor atoms, light energy slowly converted into chemical energy, stored, converted into radiant energy
initial source of phosphorescence light
radiant (light energy)
define fluorescence
- immediately emits visible light after UV light absorption
- electrical energy from wall passes through mercury vapor, mercury vapour atoms absorb electrical energy, turns into UV radiation
- UV radiation strikes fluorescent coating on inside of lightbulb, light emitted
- contains mercury
initial source of fluorescent light
electrical energy
define chemiluminescence
- light is result of chemical reaction w/ little to no heat (ex. glow sticks)
- when some chemicals mix, chemical energy from molecules before the reaction convert into light
- no electrical current needed
initial source of chemiluminescence
chemical energy
define bioluminescence
- chemical reactions in living organisms producing light (with no heat)
- occurs when 2 chemicals made by an organism mix together (jellyfish, firefly)
- used by organisms that live in dark locations
initial source of bioluminescence
chemical energy
define triboluminescence
- light is product of scratching/crushing rubbing crystals to create friction and light
- created when chemical bonds in crystals are broken
-some crystals store a lot of chemical energy, when crystal is broken, chemical energy turns into light energy and released
initial source of triboluminescence
chemical energy
define light-emitting diode (LED)
- electrical current flows through semi conductors to produce light
- when electric current flows in allowed direction, light is emitted
- les heat, more energy efficient
initial source of light-emitting diode (LED)
electrical energy
define laser
LASER- light amplification by simulated emission of radiation
- lasers produce electromagnetic waves of the same energy level in the same direction
- pure in colour, concentrated, high intensity
- never look into a laser beam
initial source of laser light
electrical energy
define nuclear light (power plants)
- unstable nucleus (ex. uranium) breaks apart and nuclear energy turns into light (called nuclear fission)
initial source of nuclear light (power plants)
nuclear energy
define nuclear light (the sun)
-hydrogen atoms in sun fuse together to create helium (called nuclear FUSION)
- nuclear energy in hydrogen atoms are released as light (product of chemical reaction)
initial source of nuclear light (the sun)
nuclear energy
what is light
form of energy visible to humans which travels in form of waves
what is a wave
a disturbance that transfer energy from one point to another
what is the crest
highest point of a wave
what is the trough
lowest point of a wave
define frequency (f)
number of times the electromagnetic fields vibrate per second
define wave length
- distance between crest to crest, or trough to trough
- length of a complete vibration
the more energy, the ______ frequent the waves and ______ the wavelength
more, shorter
the less energy, the ______ frequent the waves and ______ the wavelength
less, longer
what is the electromagnetic spectrum
range of all possible forms of electromagnetic radiation
what is the visible spectrum
part of electromagnetic spectrum visible to human eye
how do colours of the rainbow and wavelength relate?
red = longest wavelength (lowest energy)
purple = shortest wavelength (highest energy)
define reflection
when light hits surface and bounces off
define refraction
when light enters second medium (material) and bends because of a change in speed
define diffraction
light hits edge of object and bends around it
why is light brighter the closer it is your face?
- more light rays enter the eye
rules of light and matter
- light travels in straight lines unless it hits something
- when light hits an object, it can be transmitted, absorbed, or reflected depending on object
what object transmits all light
transparent
what object transmits some light
translucent
what object transmits no light
opaque
how do we see objects?
light reflects off them
what is a regular reflection?
when parallel light rays strike a smooth surface and reflect in the same direction
- image can be seen
(ex. mirror, glass, calm water)
what is a diffuse redirection?
parallel light rays strike a rough surfs r and reflect light in different directions
- cannot see an image (ex. rough water, desk, shirt)
how are concave mirrors used in flashlights
- focuses light onto one point
- helps produce parallel beam of light at light bounces off concave mirror
how are concave mirrors used in telescopes
- to collect light from a distant object and focus it
- as light hits concave mirror at parallel angle, light reflects off onto angled mirror and goes into eyepiece
how are concave mirrors used in cosmetic mirrors?
- produces an enlarged virtual image
- object must be inside focal point for it to work (close to mirror)
how are concave mirrors used in solar ovens?
- parallel rays of light are converged to one point to cook food
- all light concentrates at focal point (where food must be placed)
how are convex mirrors used in security mirrors?
- to see a larger region with a smaller camera area
