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photons of energy that travels in waves
Electromagnetic radiant energy
beam of electromagnetic radiant energy
linear distance traveled by one complete wave cycle
speed of a wave cycle
# of wave cycles occurring/second
Formula: v = c/ λ
atoms, ions or molecules have ability to absorb photons
λ at which molecule will absorb maximum amt. of energy
as “excited” ions, atoms or molecules return to ground state
What are the three forms of relesed energy?
kinetic, vibrational, radiant light (flourescence)
ratio of transmitted radiant energy (Is)/radiant incident light on sample (I)
contains everything but solute being measured
sets a new intensity of light Io
What is the amt. light absorbed dependent on?
- molecular structure
- reaction between molecules & radiant energy
The concentration of a substance is directly proportional to the amount of light absorbed or inversely proportional to the logarithm of the transmitted light.
The ratio of radiant energy transmitted divided by the radiant energy incident on the sample.
What are the lamps most commonly used for the spectrophotometer? (visible and near-infrared)
- Incandescant Tungsten
What are the lamps most commonly used for ultraviolet work on the spectrophotometer?
- Detrium-discharge lamp
- Mercury-arc lamp
Name the part by its function:
Isolation of individual wavelengths of light.
What are some examples of monochromators?
- Colored glass filters - most commonly used
- Interference filters
Convert the transmittance radiant energy into an equivalent amount of electrical energy.
What are some examples of photodetecters?
- Barrier layer cells
Contain a negatively charged cathode and a positively charged anode enclosed in a glass case. The cathode is composed of a material that acts as a resistor in the dark but emitts electrons when exposed to light.