Engineering Questions with Answers - Multiple Choice Questions

Environmental Science MCQ – Aerosols

1 - Question

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

Answer: a
Explanation: Aerosol formation by molecular nucleation leads to the production of particles with size less than 1 micron.




2 - Question

he size of aerosol particles formed mechanically is minimum 1 micron.
a) True
b) False

View Answer

Answer: a
Explanation: Due to surface tension, the minimum size of particles formed mechanically is limited to 1 micron.




3 - Question

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

Answer: b
Explanation: The Kelvin effect is a phenomenon where the vapour pressure of the droplet increases with decrease in diameter of the droplet.




4 - Question

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

Answer: c
Explanation: Based on the temperature gradient, by the effect of thermophoresis, aerosol particles move from high temperature regions to low temperature regions.




5 - Question

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

Answer: d
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 - Question

The movement of particles from region of lower vapour to high vapour molecule concentration is known as diffusiophoresis.
a) True
b) False

View Answer

Answer: b
Explanation: Movement of particles from higher vapour to low vapour molecule concentration is known as diffusiophoresis.




7 - Question

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

Answer: c
Explanation: Due to Rayleigh’s scattering shorter wavelength radiations are scattered more, and hence makes the sky appear blue.




8 - Question

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

Answer: d
Explanation: Light intensity decreases when passed through a suspension due to scattering and absorption of light by suspended particles.




9 - Question

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

Answer: d
Explanation: Inertial methods such as particle acceleration, pulsation and multi-cyclones are used to measure size of aerosol particles larger than 5 microns.




10 - Question

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

Answer: b
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 - Question

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

Answer: d
Explanation: Aerosol is a colloid formed by the presence of fluid or solid particles suspended in the air/atmosphere.




12 - Question

Aerosols contribute to global warming.
a) True
b) False

View Answer

Answer: b
Explanation: Aerosols help in scattering radiations from the sun back into outer space and help cool down the atmosphere.




13 - Question

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

Answer: c
Explanation: Aerosol consists of solid/fluid particles of size ranging between 0.01-1 microns.




14 - Question

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

Answer: b
Explanation: The aero-dynamic diameter gives the equivalent diameter of a sphere having the same volume as that of the aerosol.

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