Environmental Science Multiple Choice Questions 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
Answer: a
Clarification: 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
Answer: a
Clarification: 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
Answer: b
Clarification: 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
Answer: c
Clarification: 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
Answer: d
Clarification: 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
Answer: b
Clarification: 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
Answer: c
Clarification: 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
Answer: d
Clarification: 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
Answer: d
Clarification: 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