1. Greenhouse effect takes place because of the blanketing effect of carbon dioxide allowing
(a) short wave length of radiations to pass through it
(b) long wave length of radiations to pass through it
(c) both short wave and long wave radiations to pass through it.
(d) neither long nor short length radiations to pass through it
2. Ozone hole is dangerous because it makes us more exposed to
(a) ultraviolet rays.
(b) cosmic rays.
(c) infrared rays.
(d) ultrasound rays.
3. What is photochemical smog?
(a) Suspension of carbon particles and dust
(b) Chlorophyll of leaves
(c) Silver compound
(d) hydrocarbons and oxides of nitrogen
4. CO concentration in a mine working should be
(a) < 25 ppm
(b) < 50 ppm
(c) < 100 ppm
(d) < 150 ppm
5. Oil-rich and oil-lean compositions of ANFO produce the following gases, respectively:
(a) NH₃ and H₂S
(b) SO₂ and H₂
(c) CO and NOx
(d) NOx and CO₂
6. The permissible limit for respirable silica dust with particle size below 5 microns in a mine is (in mg/m³) given by
(a) 0.05
(b) 0.01
(c) 0.10
(d) None of these
7. The maximum permissible noise level for 8 hr working shift per day as per DGMS is
(a) 95 dB
(b) 92 dB
(c) 85 dB
(d) 90 dB
8. Indian standard for safe drinking water as regard to its pH and hardness (mg/1 CaCO3), respectively are
(a) 7.0 to 8.5, < 300
(b) 6.5 to 8.5, < 300
(c) 6.0 to 7.0, < 500
(d) 7.0 to 8.0, > 200
9. Peak particle velocity due to blasting should be restricted to
(a) 12 mm/sec
(b) 25 mm/sec
(c) 50 mm/sec
(d) 32 mm/sec
10. Acid rains occur due to the following reasons:
(a) Inflammable gases forming CFC
(b) H₂O forming acids
(c) Ozone holing
(d) SO₂ released in atmosphere forming sulphuric acid
Answer
1. (a) Greenhouse gases in the atmosphere (such as water vapour and carbon dioxide) absorb most of the Earth's emitted long wave infrared radiation, which heats the lower atmosphere. In turn, the warmed atmosphere emits long wave radiation, some of which radiates toward the Earth's surface, keeping our planet warm and generally comfortable. Increasing concentrations of greenhouse gases such as carbon dioxide and methane increase the temperature of the lower atmosphere by restricting the outward passage of emitted radiation, resulting in "global warming," or, more broadly, global climate change.
2. (a) The ozone layer is a region of high ozone concentration in the stratosphere, 15 to 35 kilometres above Earth's surface. The ozone layer acts as an invisible shield and protects us from harmful ultraviolet (UV) radiation from the sun. In particular, the ozone layer protects us from the UV radiation, known as UV-B, which causes sunburn. Long-term exposure to high levels of UV-B threatens human health and damages most animals, plants and microbes, so the ozone layer protects all life on Earth.
3. (d) Photochemical smog is a brownish-gray haze caused by the action of solar ultraviolet radiation on an atmosphere polluted with hydrocarbons and oxides of nitrogen. It contains anthropogenic air pollutants, mainly ozone, nitric acid, and organic compounds, which are trapped near the ground by temperature inversion.
4. (b)
5. (d)
6. (a) The NIOSH recommended exposure limit (REL) for respirable crystalline silica is 0.05 mg/m³ (50 µg/m³) as a TWA for up to 10 hours/day during a 40-hour work week.
7. (d) In India Directorate General of Mines Safety (DGMS) circular no. 18 Tech 75 has prescribed the permissible noise level of 90 dB (A) in a shift of 8 hours for unprotected ear, whereas the “warning limit” as per DGMS has been fixed at 85 dB (A) and 90 dB (A) is the “danger limit”.
8. (b)
9. (b) Most of the frequencies were ranging between 8-25Hz (74 %)
10. (d) Acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. These substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.
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