Assertion: BOD of a river polluted by sewage is more than 20 ppm.
Reason: Polluted river contains excess of organic matter.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
A.
If both assertion and reason are true and reason is the correct explanation of assertion.
Degree of impurity of water due to organic matter is measured in terms of BOD (Biochemical oxygen demand). BOD is the oxygen in milligrams required for five days in one litre of water at 20°C for the microorganisms to metabolise organic waste. It is measured in the milligrams of oxygen taken up in one litre of sewage. The effluent that is legally allowed to be discharged into a river or stream should be such that BOD at 20°C should not be more than 20 ppm, i.e., 20 mg per litre.
Which country has the greatest contribution for the hole formation in ozone layer?
USA
Germany
Russia
Japan
Photosynthetic Active Radiation (PAR) has the following range of wavelengths
400- 700 nm
450- 950 nm
340- 450 nm
500- 600 nm
Which of the following statement is correct about DDT
It is a biomagnifying biodegradable pollutant
It is non biomagnifying biodegradable pollutant
It is biomagnifying non biodegradable pollutant
It is not a pollutant
Assertion: Secondary air pollutants are formed by interaction among the primary pollutants and are more toxic.
Reason: DDT is a secondary air pollutant.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
The gases that produce green house gases are
CH4, CFCs, CO2
CO2, N2O, H2
CFCs, NO2, O2
CO2, N2, water vapour
CO is a pollutant because
it reacts with O2
it inhibits glycolysis
it reacts with haemoglobin
it makes nervous system inactive
A large quantity of urban sewage is drained into nearby village river. Which among the given conditions would happen after mixing of sewage into the river
(i) Biochemical oxygen demand (BOD) of receiving water body increases.
(ii) Dissolved oxygen of receiving water body decreases.
(iii) It will not cause mortality among fishes and other aquatic creatures.
(iv) It will lead to nutrient enrichment of receiving water body.
(i), (ii) and (iii)
(i), (ii) and (iv)
(ii) and (iii) only
(iii) and (iv) only
One greenhouse gas contributes 14% to total global warming and another contributes 6%. These are respectively identified as
N2O and CO2
CFCs and N2O
methane and CO2
methane and CFCs
