The intensity produced by a long cylindrical light source at a small distance r from the source is proportional to
(a) 1/r2
(b)1/r3
(c) 1/r
(d) none of these.
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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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A point source of light is placed at a distance, of 2 f from a converging lens of focal length 1 The intensity on the othe
The correct answer is (c) 2 f EXPLANATION: The intensity of the light on the other side is maximum where the image of the point source is formed. Here u = -2f, f...
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A light source emits monochromatic light of wavelength 555 nm. The source consumes 100 W of electric power
Overall luminous efficiency =Total luminous flux / Power input =35x685/100 = 239.75 lumen/W
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Light passes through a closed cylindrical tube containing a gas. If the gas is gradually pumped out, the speed of light inside the tube will
(a) increase
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Light from a point source falls on a small area placed perpendicular to the incident light. If the area is
The illuminance will not change.
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A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 1/2 m away,
The correct answer is (2) l∝ 1/r2
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A small object is placed at the centre of the bottom of a cylindrical vessel of radius 3 cm and height 4 cm
How it comes cot r = 3/4 ?
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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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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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