The intensity of gamma radiation from a given source is I. On passing through 36 mm of lead, it is reduced to 1/8. The thickness of lead which will reduce the intensity to 1/2 will be
(1) 6 mm
(2) 9 mm
(3) 18 mm
(4) 12 mm
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What is the percentage of photosynthetically active radiation (PAR), in the incident solar radiation.
(b) 50% Out of total incident solar radiation, about fifty percent of it forms photosynthetically active radiation or PAR.
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Wavelength of radiation incident on a surface is 850 nm. Will the surface become visible when exposed to this radiation? Explain.
As we know, the range of wavelength of visible radiation is from 400 nm to 700 nm. The radiation having wavelength greater than 700 nm is termed as infra-red radiations...
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The inverse square law of intensity (i.e., the intensity ∝ 1/r^2) is valid for a (a) point source (b) line source
(a) point source EXPLANATION: Only for a point source the intensity can be written as I = E/4πr², where E is the strength of the source. Hence E ∝ 1/r².
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Two coherent sources of different intensities send waves which interfere. The ratio of maximum intensity to the minimum intensity is 25.
The correct answer is (c) 9 : 4 EXPLANATION: Since the resultant field at a point is given as E₀² = E₁² + E₂² + 2E₁E₂ cosδ Where E₁ and E₂ = amplitudes...
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The intensity produced by a long cylindrical light source at a small distance r from the source is proportional to
The correct answer is (c) 1/r
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When an unpolarized light of intensity I_0 is incident on a polarizing sheet, the intensity of the light which does not get transmitted is
The correct answer is (1) When unpolarised light of intensity Io is incident on a polarizing sheet, only Io/2 is transmitted.
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A heated body emits radiation which has maximum intensity near the frequency v0.
The correct answer is (a) (c) (a) the maximum intensity of radiation will be near the frequency 2v0 (c) the total energy emitted will increase by a factor of 16.
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When the intensity of a light source is increased, (a) the number of photons emitted by the source in unit time increases
(a) the number of photons emitted by the source in unit time increases (b) the total energy of the photons emitted per unit time increases
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A freshly prepared radioactive source of half-life 2h emits radiation of intensity which is 64 times the permissible safe level.
(b) The minimum time after which it would be possible to work safely with this source is 12h.
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Lead, ingested or inhaled, is a health hazard. After the addition of lead to petrol has been banned, what still are the sources of lead poisoning ?
(b) Smelting units and paints are the source of the lead poisoning.
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