Light from a point source falls on a small area placed perpendicular to the incident light. If the area is rotated about the incident light by an angle of 60°, by what fraction will the illuminance change ?
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Which of the following can make a parallel beam of light when light from a point source is incident on it?
(a) Concave mirror as well as convex lens
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A small amount of silica gel and a small amount of anhydrous calcium chloride are placed separately in two beakers containing water vapour.
[Hint : Silica gel : Adsorption, Anhydrous CaCl2 : Absorption, as it forms Ca- Cl2.2H2O]
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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 from a point source falls on a screen. If the separation between the source and the screen is increased by 1%,
The correct answer is (c) 2%
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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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A photographic plate is placed directly in front of a small diffused source in the shape of a circular disc
The correct answer is (c) 24 s
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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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What type of wavefront will emerge from a (i) point source, and (ii) distant light source?
Wavefront from a point source – spherical Wavefront from a distant light source – plane.
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Assertion (A) : Small glass beads fixed on traffic signals glow brightly when light falls upon them.
(a) Both of the statements are correct and statement 2 is also correct explanation for statement 1. Total internal reflection is an optical phenomenon that happens when a ray of...
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