What is Fluorescence Spectrophotometry?
Fluorescence spectrophotometry is a technique used to measure the intensity of light emitted by a sample when it is excited by a specific wavelength of light. The sample, typically a dilute solution, is first irradiated with a beam of light of a specific wavelength (excitation wavelength) that is absorbed by the sample, which causes the molecules in the sample to become excited and release energy in the form of light (emission). The emitted light is then detected and analyzed by a spectrophotometer. The process is also known as fluorescence spectroscopy. This technique is useful for detecting small amounts of a specific compound or protein, studying protein-ligand interactions, and for studying conformational changes in proteins.
Also Read: Fluorescence Spectrophotometry – Definition, Principle, Parts, Advantages, Uses
MCQ on Fluorescence Spectrophotometry
1. What type of radiation is absorbed by a molecule in order for fluorescence to occur?
a) Visible light
b) Ultraviolet light
c) Infrared light
d) X-ray
2. What type of radiation is emitted by a molecule during fluorescence?
a) Visible light
b) Ultraviolet light
c) Infrared light
d) X-ray
3. What is the process by which a molecule becomes excited and then releases energy in the form of fluorescence called?
a) Absorption
b) Emission
c) Excitation
d) Fluorescence
4. What type of instrument is used to measure fluorescence?
a) Spectrophotometer
b) Spectrometer
c) Fluorometer
d) Photometer
5. What type of sample is best suited for fluorescence spectrophotometry?
a) Solid
b) Liquid
c) Gas
d) Dilute solutions
6. What is the difference between fluorescence and phosphorescence?
a) Fluorescence is immediate and phosphorescence is delayed
b) Fluorescence is weak and phosphorescence is strong
c) Fluorescence is temporary and phosphorescence is permanent
d) Fluorescence is in UV and phosphorescence is in the visible light range
7. What is the lifetime of the excited state of a molecule in fluorescence?
a) Microseconds
b) Milliseconds
c) Seconds
d) Minutes
8. What is the quantum yield of a molecule in fluorescence?
a) The ratio of the number of photons emitted to the number of photons absorbed
b) The ratio of the number of photons absorbed to the number of photons emitted
c) The ratio of the energy absorbed to the energy emitted
d) The ratio of the energy emitted to the energy absorbed
9. What is the Stokes Shift in fluorescence?
a) The difference in energy between the absorbed and emitted photons
b) The difference in wavelength between the absorbed and emitted photons
c) The difference in intensity between the absorbed and emitted photons
d) The difference in polarization between the absorbed and emitted photons
10. What is the difference between fluorescence and absorption spectrophotometry?
a) Fluorescence measures the emission of light while absorption measures the absorption of light
b) Fluorescence measures the intensity of light while absorption measures the wavelength of light
c) Fluorescence measures the polarization of light while absorption measures the energy of light
d) Fluorescence measures the fluorescence while absorption measures the absorption
11. What is the difference between fluorescence and Raman spectroscopy?
a) Fluorescence measures the emission of light while Raman measures the scattering of light
b) Fluorescence measures the intensity of light while Raman measures the wavelength of light
c) Fluorescence measures the polarization of light while Raman measures the energy of light
d) Fluorescence measures the fluorescence while Raman measures the Raman scattering
12. What is the difference between fluorescence and nuclear magnetic resonance spectroscopy?
a) Fluorescence measures the emission of light while NMR measures the magnetic properties of nuclei
b) Fluorescence measures the intensity of light while NMR measures the wavelength of light
c) Fluorescence measures the polarization of light while NMR measures the energy of light
d) Fluorescence measures the fluorescence while NMR measures the nuclear spin and magnetic properties of atoms and molecules.
13. Why is a fluorescence filter used in a fluorescence spectrophotometer?
a) To absorb unwanted light
b) To transmit a specific wavelength range of light
c) To scatter light
d) To polarize light
14. What is the purpose of a quencher in fluorescence spectrophotometry?
a) To increase the fluorescence intensity
b) To decrease the fluorescence intensity
c) To change the wavelength of the emitted light
d) To change the polarization of the emitted light
15. Why is fluorescence spectrophotometry useful in biological research?
a) It allows for the detection of very small amounts of a specific molecule
b) It allows for the study of protein-ligand interactions
c) It allows for the study of conformational changes in proteins
d) All of the above
Answer Key
- b) Ultraviolet light
- a) Visible light
- c) Excitation
- c) Fluorometer
- d) Dilute solutions
- a) Fluorescence is immediate and phosphorescence is delayed
- a) Microseconds
- a) The ratio of the number of photons emitted to the number of photons absorbed
- b) The difference in wavelength between the absorbed and emitted photons
- a) Fluorescence measures the emission of light while absorption measures the absorption of light
- a) Fluorescence measures the emission of light while Raman measures the scattering of light
- a) Fluorescence measures the emission of light while NMR measures the magnetic properties of nuclei
- b) To transmit a specific wavelength range of light
- b) To decrease the fluorescence intensity
- d) All of the above
