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Class 10 Class 12

dB is a standard abbreviation used for the quantitative expression of

• the density of bacteria in a medium

• a particular pollutant

• the dominant Bacillus in a culture

• a certain pesticide

B.

a particular pollutant

Noise pollution is a physical form of pollution that affects the receiver directly. dB (decibel) is a standard abbreviation used for the quantitative expression of noise. Noise or pollutant sound has a value of 80 dB and above, it harms hearing system. The WHO has fixed 45 dB as the safe noise level for city

Noise pollution is a physical form of pollution that affects the receiver directly. dB (decibel) is a standard abbreviation used for the quantitative expression of noise. Noise or pollutant sound has a value of 80 dB and above, it harms hearing system. The WHO has fixed 45 dB as the safe noise level for city

In the scrubber in the electrostatic precipitator the gases are passed through :
• filter
• lime
• spray of water
• both 2 and 3

D.

both 2 and 3

Which of the following pollutants is not produced by exhaust of motor vehicles ?
• CO
• Hydrocarbon
• Fly-ash
• NO

C.

Fly-ash

Ozone depletion will cause :
• Forest fire
• Pneumonia
• Increased incidence of skin cancer
• None of these

C.

Increased incidence of skin cancer

What is the term for the inflammation of cornea due to high absorption of UV-B radiation :
• myopia
• snow blindness
• biomagnification
• None of the above

B.

snow blindness

The meaning of BOD is :
• Bacterial oxygen demand
• Biological optimum density
• Biochemical oxygen demand
• Bioorganisation decay

C.

Biochemical oxygen demand

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