CIULLA_INSTRUMENTATION & ANALYTICAL PRINCIPLES
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referred to as the distance traveled by one complete wave cycle (distance between two successive crests)
Wavelength
Wavelength is measured in _____
nanometers (nm)
characterized as a spectrum from short wavelength to long wavelength
Radiant energy
order of wavelengths from shortest to longest
Gamma ray X-ray UV Visible Infrared Microwave Radio
Two properties of electromagnetic radiation
wave-like particle-like
T/F: The shorter the wavelength, the greater the energy
TRUE The shorter the wavelength, the greater the energy (also the greater number of photons
Visible light wavelength
400-700 nm
What is detected when all visible wavelengths of light are combined?
White light
Visible color
wavelength of light transmitted (not absorbed) by an object
the particles of light
photons
three ways by which an atom becomes excited upon absorbing a photon
• electron is moved to a higher energy level • the mode of the covalent bond vibration is changed • rotation around covalent bonds is changed
When energy is absorbed as a photon, an electron is moved to a higher energy level where it is _________.
unstable
T/F: An excited electron is unstable and will return to ground state
TRUE
An excited electron emits energy in the form of _____.
Light
Absorption or emission of energy forms a ________ that is characteristic of a molecule and can help identify a molecule.
line spectrum
an instrument used to determine the concentration of a light-absorbing analyte in solution.
spectrophotometer
T/F: An analyte may absorb, transmit and reflect light to varying degrees but always of a characteristic nature for the analyte
TRUE
Components of a Spectrophotometer
• power supply • light source • entrance slit • monochromator • exit slit • cuvet/sample cell • photodetector • readout device
component of a spectrophotometer which produces an intense, reproducible, constant beam of light
light source (exciter lamp)
Types of incandescent lamps
tungsten deuterium
type of incandescent lamp regarded as most common and is used in visible and infrared regions
tungsten
type of incandescent lamp used in UV region
deuterium
T/F: Changing the light source in a spectrophotometer changes the angle of the light striking the monochromator
TRUE Recalibration is a must upon changing light source.
a component of the spectrophotometer which converts the electromagnetic radiation transmitted by a solution into an electric signal
Photodetector