3.1: Natures & Sources of Light Flashcards
(21 cards)
Luminous Objects
Ability to give off their own light
Non-Luminous Objects
Do NOT give off their own light, reflect of luminous objects
Electromagnetic Waves
how energy travels through space
- energy in form of wave, associated with electric and magnetic fields
- travel through vacuum at speed of light or medium
What is a medium?
any physical substance through which energy can be transferred
Wavelength
distance between highest points (two crests)
Frequency
how fast wavelengths travel
Electromagnetic Spectrum
arrangement of all EM waves according to wavelengths and frequency
Describe connection between energy and wavelengths/frequency
- Low energy –> longer wavelength = low frequency
- High energy –> shorter wavelength = high frequency
Name 7 types of EM waves (low to high)
Radio Waves
Microwaves
Infrared Light
Visible Light
UV Light
X-rays
Gamma rays
Visible Spectrum
continuous sequence of colours that form visible white light
Visible Light
Any electromagnetic wave that the human eye can see
Name the order of visible light from lowest to highest energy
Red
Orange
Yellow
Green
Blue
Indigo
Violet
How are sources of Light formed?
- all light sources have atoms in the material that absorb energy in an excited state
- excited atoms RELEASE the energy in form of light
Incandescent Light
- light emitted by very HOT object
- electrical energy generates the HEAT that excites the atoms to release light
(Ex. lamp - wire gets hot and glows when electric current runs through
Electric Discharge
- emits light from HEATED GAS or vapour
- electric current passes through vapour and excites atom
- emits yellow light (ex. sodium vapour bulb)
What is Luminescence?
light generated without heating
Fluorescence
- exposure of mercury vapour with inert gas to excite mercury atoms
- produces UV light that is absorbed by phosphor to emit light
(ex. light bulb)
Phosphorescence
- same as fluorescent but excited atoms retain energy for longer
- emit light after UV absorbed
(ex. glow in dark charged in sun)
Chemiluminescene
- light generated by energy released from chemical reaction
(ex. glowsticks)
Bioluminescence
- light produced from living organisms
- chemical reactions in living cells produce light
(ex. jellyfish, firefly)
Light-Emitting-Diode (electroluminescence)
- electric device that produces light when electrically passes through
- moves electrons through a semiconductor, releasing energy as light
(ex. LED Lights - use less energy, last longer)
