This set of Environmental Science Multiple Choice Questions & Answers (MCQs) focuses on “Aerosols”.
1. Formation of aerosols by nucleation produces particles of size __________
a) Less than 0.1 micron
b) Greater than 0.1 micron
c) Less than 1 micron
d) Greater than 1 micron
View Answer
Explanation: Aerosol formation by molecular nucleation leads to the production of particles with size less than 1 micron.
2. The size of aerosol particles formed mechanically is minimum 1 micron.
a) True
b) False
View Answer
Explanation: Due to surface tension, the minimum size of particles formed mechanically is limited to 1 micron.
3. What is the statement of the Kelvin effect in fluid droplets?
a) Vapour pressure about a droplet decreases with decrease in diameter of the droplet
b) Vapour pressure about a droplet increases with decrease in diameter of the droplet
c) Vapour pressure of the droplet is independent of the diameter of the droplet
d) Vapour pressure of the droplet varies with the diameter of the droplet as well as the temperature
View Answer
Explanation: The Kelvin effect is a phenomenon where the vapour pressure of the droplet increases with decrease in diameter of the droplet.
4. When a given gas has a temperature gradient, the aerosol particles move from higher temperature regions to low temperature regions. This effect is known as __________
a) Photophoresis
b) Diffusiophoresis
c) Thermophoresis
d) Diffusiophoresis or Thermophoresis
View Answer
Explanation: Based on the temperature gradient, by the effect of thermophoresis, aerosol particles move from high temperature regions to low temperature regions.
5. Particle movement due to photophoresis depends on _________
a) Shape and size of the particle
b) Optical properties of the particle
c) Wavelength and intensity of incident light
d) All of the mentioned
View Answer
Explanation: Particle movement due to photophoresis depends on the shape, size and optical properties of the particle, as well as wavelength and intensity of incident light.
6. The movement of particles from region of lower vapour to high vapour molecule concentration is known as diffusiophoresis.
a) True
b) False
View Answer
Explanation: Movement of particles from higher vapour to low vapour molecule concentration is known as diffusiophoresis.
7. Which of the following scattering phenomena is responsible for the blue colour of the sky?
a) Mie scattering
b) Diffraction
c) Rayleigh scattering
d) All of the mentioned
View Answer
Explanation: Due to Rayleigh’s scattering shorter wavelength radiations are scattered more, and hence makes the sky appear blue.
8. When light is passed through a suspension, it’s intensity decreases due to _________
a) Both scattering and diffraction
b) Both diffraction and absorption
c) Absorption only
d) Both scattering and absorption
View Answer
Explanation: Light intensity decreases when passed through a suspension due to scattering and absorption of light by suspended particles.
9. What is/are the inertial method(s) used to measure size of aerosol particles?
a) Particle acceleration method
b) Pulsation method
c) Multi cyclone
d) All of the mentioned
View Answer
Explanation: Inertial methods such as particle acceleration, pulsation and multi-cyclones are used to measure size of aerosol particles larger than 5 microns.
10. What does CNC stand for in the context of aerosol particles?
a) Cloudy nucleic condensation
b) Condensation nucleus counter
c) Chemical nucleic coagulation
d) Cloudy nucleic coagulation
View Answer
Explanation: To measure the number concentration of aerosol particles, we use a condensation nucleus counter which counts particles of even 0.003 micron diameter.
11. What type of colloid is an aerosol?
a) Solid in gas
b) Gas in solid or fluid
c) Fluid in gas
d) Fluid or solid in gas
View Answer
Explanation: Aerosol is a colloid formed by the presence of fluid or solid particles suspended in the air/atmosphere.
12. Aerosols contribute to global warming.
a) True
b) False
View Answer
Explanation: Aerosols help in scattering radiations from the sun back into outer space and help cool down the atmosphere.
13. What is the size of the particles categorised as aerosols?
a) Greater than 1 micron
b) Less than 1 micron
c) Between 0.01-1 micron
d) Less than 0.01 micron
View Answer
Explanation: Aerosol consists of solid/fluid particles of size ranging between 0.01-1 microns.
14. What does the aerodynamic diameter of an aerosol indicate?
a) Size of the aerosol particle when floating in air
b) Equivalent diameter of a sphere having same volume as that of the aerosol
c) Average diameter of aerosol particles present in unit volume of air
d) Maximum size of aerosol particle that can float in the air
View Answer
Explanation: The aero-dynamic diameter gives the equivalent diameter of a sphere having the same volume as that of the aerosol.
Sanfoundry Global Education & Learning Series – Environmental Science.
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