Question
Which city receives the highest cosmic radiation amongst the following ?
Answer: Option D
Answer: (d)
The total annual external dose from sources in soil and cosmic rays in Mumbai, Kolkata, Chennai, Delhi and Bengaluru is 0.484, 0.81, 0.79, 0.70 and 0.825 milligray respectively. Gray is a unit for absorbed dose; when the radiation energy imparted to a kg of material is one joule, it is called a gray.
Since gray is very large, milligrays (one-thousandth of a gray), and microgray (one-millionth of a gray), are commonly used. Cosmic rays come from outer space. Their intensity at a place depends on the altitude. Cosmic rays alone contribute 0.28 milligrays at the first three cities as they are at sea level; the column of air helps to reduce their intensity.
At high altitudes, the protection from the column of air is less. The cosmic ray contributions are higher at 0.31 milligray and 0.44 milligray respectively at Delhi and Bengaluru as these cities are at altitudes of 216 metres and 921 metres. Air passengers receive 5 micrograys per hour from cosmic rays. Parts of Kerala and Tamil Nadu are high background radiation areas (HBRA) because of the presence of large quantities of monazite in the soil.
Thorium content in monazite ranges from 8-10.5 per cent. Researchers found that the radiation levels in 12 Panchayats in Karunagappally varied between 0.32 to 76 milligrays per year; the levels in 90 per cent of over 71,000 houses were more than one milligray per year.
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Answer: (d)
The total annual external dose from sources in soil and cosmic rays in Mumbai, Kolkata, Chennai, Delhi and Bengaluru is 0.484, 0.81, 0.79, 0.70 and 0.825 milligray respectively. Gray is a unit for absorbed dose; when the radiation energy imparted to a kg of material is one joule, it is called a gray.
Since gray is very large, milligrays (one-thousandth of a gray), and microgray (one-millionth of a gray), are commonly used. Cosmic rays come from outer space. Their intensity at a place depends on the altitude. Cosmic rays alone contribute 0.28 milligrays at the first three cities as they are at sea level; the column of air helps to reduce their intensity.
At high altitudes, the protection from the column of air is less. The cosmic ray contributions are higher at 0.31 milligray and 0.44 milligray respectively at Delhi and Bengaluru as these cities are at altitudes of 216 metres and 921 metres. Air passengers receive 5 micrograys per hour from cosmic rays. Parts of Kerala and Tamil Nadu are high background radiation areas (HBRA) because of the presence of large quantities of monazite in the soil.
Thorium content in monazite ranges from 8-10.5 per cent. Researchers found that the radiation levels in 12 Panchayats in Karunagappally varied between 0.32 to 76 milligrays per year; the levels in 90 per cent of over 71,000 houses were more than one milligray per year.
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