Question 1 of 5
Which layer of the atmosphere reflects back the radio waves that are transmitted from the earth?
A. Troposphere
B. Stratosphere
C. Ionosphere
D. Mesosphere
A
Troposphere
B
Stratosphere
C
Ionosphere
D
Mesosphere
Why: The **Ionosphere** is the atmospheric layer that reflects radio waves back to Earth due to its high concentration of ionized particles. These ions, created by solar radiation, refract and reflect radio frequencies, enabling long-distance communication. The troposphere is the lowest layer with weather phenomena; stratosphere contains the ozone layer; mesosphere burns meteors. Thus, option C is correct.[1]
Question 2 of 5
The main constituents of Acid rain are
A. Nitric acid and acetic acid
B. Nitric acid and sulfuric acid
C. Sulfuric acid and acetic acid
D. Acetic acid and hydrochloric acid
A
Nitric acid and acetic acid
B
Nitric acid and sulfuric acid
C
Sulfuric acid and acetic acid
D
Acetic acid and hydrochloric acid
Why: Acid rain primarily consists of **sulfuric acid (H2SO4)** and **nitric acid (HNO3)**, formed from atmospheric SO2 and NOx emissions reacting with water vapor. These acids lower the pH of precipitation below 5.6, impacting ecosystems. Acetic acid and hydrochloric acid are minor or not primary contributors in this context. Option B matches the standard composition.[1]
Question 3 of 5
Match LIST-I with LIST-II
LIST-I (Atmospheric component)
(A) Nitrogen
(B) Sulphur dioxide
(C) Aerosols
(D) Ozone
LIST-II (Role)
(I) Hypoxyotic anticline
(II) Photochemical interaction
(III) Retards re-radiation (Greenhouse Effect)
(IV) Acid rain
(A) A-III, B-II, C-I, D-IV
(B) A-I, B-III, C-II, D-IV
(C) A-III, B-IV, C-I, D-II
(D) A-IV, B-II, C-I, D-II
A
A-III, B-II, C-I, D-IV
B
A-I, B-III, C-II, D-IV
C
A-III, B-IV, C-I, D-II
D
A-IV, B-II, C-I, D-II
Why: The correct matching is: Nitrogen (A) retards re-radiation through greenhouse effect (III) as N2O contributes to it; Sulphur dioxide (B) causes acid rain (IV); Aerosols (C) are hygroscopic and aid cloud formation (I); Ozone (D) undergoes photochemical interactions (II) leading to smog formation. Option C matches this pairing exactly[2].
Question 4 of 5
Which of the following were the characteristics of the prebiotic primitive Earth?
A. Presence of CO2
B. Presence of CH4
C. Presence of H2O vapour
D. Presence of O2
Choose the correct answer from the options given below:
A
A, B and C only
B
B, C and D only
C
A, B, C and D
D
A and D only
Why: The prebiotic primitive Earth atmosphere was reducing, characterized by presence of CO2 (A), CH4 (methane, B), and H2O vapour (C), but lacked free O2 (D) which appeared later due to photosynthesis. Thus, A, B, and C only is correct[3].
Question 5 of 5
Choose the correct statements.
A. Dissolution of oxygen in surface water changes with change in temperature during extreme summer and winters.
B. Dissolved oxygen and BOD have inverse relationship in sewage water.
C. Chemical oxygen demand is always higher than BOD in sewage water.
D. More saline water will have less conductivity.
(A) A and B only
(B) A, B and D only
(C) A, B, C and D
(D) A, B and C only
A
A and B only
B
A, B and D only
C
A, B, C and D
D
A, B and C only
Why: A is correct: Oxygen solubility decreases in warmer summer water and increases in colder winter water. B is correct: Higher BOD means more oxygen consumed by microbes, lowering DO. C is correct: COD measures total oxidizable matter, always ≥ BOD. D is incorrect: Salinity increases conductivity. Thus, A, B, C only (option D)[2].
