Chemistry- Light Flashcards
(20 cards)
continuous spectrum
- when white light is passed through a prism
- contains all the wavelengths of visible light
emission spectrum
- light emitted from excited gas
- an electron gains energy as it moves away from nucleus
- eventually, it will return to its initial location (ground state) and emit energy
excited electron
unstable
Wavelength (λ)
- distance from crest to crest
- nm/m
- as it decreases, frequency increases (inversely proportional)
Frequency (v)
of waves that pass a given point per second (Hz)
How to calculate λ or v
- c = λv
- c = 3.00 X 10^8 m/s
Photoelectric effect
- electrons are emitted from a metal when light shines on it
- depends of frequency NOT intensity
- Ephoton=hv
- E (energy) and h (Planck’s constant- 6.626 X 10^-34 J S)
Max Planck (1900)
energy is quantized, NOT continuous
Louis de Broigle (1924)
- electron is a particle but moves as though it is a wave
- it is possible to know the exact location of an electron
- an electron oscillates up and down like a standing wave
Werner Heisenberg
electron DOES NOT move like a wave, much more complicated
Heisenberg Uncertainty Principle
it is impossible to know the exact momentum and location of an electron; the more you know about one electron, the less you know about the other
Wave Particle Duality
- shows an atom as an electron cloud that gets less dense as the distance from the nucleus increases
Electromagnetic Radiation
- one of the ways that energy travels through space
- 4 characteristics: wavelength, frequency, amplitude, speed
Visible light from shortest to longest
Violet, Blue, Green, Yellow, Orange, Red
EM spectrum shortest to longest wavelength
Gamma – X ray – Ultraviolet – Visible – Infrared – Microwave – Radio waves
Energy as wavelength decreases
It increases (Blue has a shorter wavelength and more energy than red)
Range of visible light
380 - 750 nm
Light with Frequency lower than threshold
no electrons are emitted
Light with Frequency higher than threshold
- number of electrons emitted increases with the intensity of light
- kinetic energy of emitted electron increases linearly with frequency of light
diffraction of NaCi
- bright spots are produced from CONSTRUCTIVE INTERFACE
- dark spots are produced from DESTRUCTIVE INTERFACE
