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

Higher EnergyLower Energy

LINK

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