toipc: emission spectrum. flame test demo when matter is heated it gives off light –example: fire...
TRANSCRIPT
TOIPC: EMISSION SPECTRUM
Flame Test DEMO
• When Matter is heated it gives off light– Example: fire work, pyrotechnics, flame test
– The heat energy absorbed by the metal ions
excites the atoms’ electrons– The absorbed energy is
eventually released in the
form of light
• Another example– Example: light bulb– The electrical energy
absorbed by the filament
excites the atoms’ electrons– The absorbed energy is
eventually released in the
form of light
Why do we see colors?Where do they come from?
What are they?
CONTINUOUS (WHITE LIGHT) SPECTRA
When normal white light (such as light from the sun or a light bulb) is passed through a prism (or rain drop), the light separates into a continuous
spectrum of colors
PRISM
• White light is broken into 7 spectral lights, what are they?
ROY G BIV
Originally Scientists (even Newton) thought that light was made up of particles but this couldn’t’ explain why different color were
refracted differentNOTICE: Violet bends a lot more than Red
Light made up of waves
Basic Wave Vocab
Transverse vs Longitudinal Waves
Transverse
Longitudinal
Wavelength vs. Frequency• WAVELENGTH = distance light travels to
complete 1 cycle• FREQUENCY = number of cycles
completed in 1 second
• The colors we see have different wave lengths• Red = longer wave length• Violet = shorter wave length
Which one has the higher frequency?
,higher frequency
,lower frequency
Wavelength and Frequency have an inverse relationship
You can even calc. the Wave Velocity
• speed of wave in direction is traveling
• Velocity = wavelength x frequency
Velocity =
Scientists realized that many light waves couldn’t been seen
with the naked
Electromagnetic Spectrum
THE MYSTERY OF EMISSION- LINE SPECTRUM
Solids, liquids, and dense gases emit light of all wavelengths, without any gaps = Continuous Spectrum
Thin gases emit light of only a few wavelengths = Emissions or Bright Line Spectrum
Bright Line Spectrum
• Atoms cannot emit energy continuously, rather they emit energy in precise quantities
• How does this work– Electrons absorb energy (they get EXCITED)
and “jump” to a higher energy level– After a short time, they “fall” back to lower
energy level, giving off a specific amount of energy (a quantum of energy) in the form of a photon (light)
Scientists of the 19th century quickly figured out that each element generates its own
unique set of wavelengths of emissions and absorptions due to it’s unique electron
configuration. Hydrogen:
Neon line spectra