Light from a point source falls on a screen. If the separation between the source and the screen is increased by 1%, the illuminance will decrease (nearly) by
(a) 0.5%
(b) 1%
(c) 2%
(d) 4%.
1 Answers
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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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Which separation techniques will apply for the separation of the following? (a) Sodium chloride from its solution in water
(a) Crystallization or Evaporation. (b) Sublimation. (c) Centrifugation or Sedimentation. (d) Chromatography. (e) Centrifugation. (f) Separating funnel. (g) Hand-picking. (h) Magnetic separation. (i) Winnowing. (j) Centrifugation.
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A source of sound moves towards an observer. (a) The frequency of the source is increased.
(c) The wavelength of the sound in the medium towards the observer is decreased. EXPLANATION: When the source of sound moves towards an observer neither the frequency of the sound nor the...
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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 small area placed perpendicular to the incident light. If the area is
The illuminance will not change.
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When the separation between two charges is increased, the electric potential energy of the charges (a) increases
(d) may increase or decrease.
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The separation between the plates of a charged parallel-plate capacitor is increased.
The correct answer is (b) (c) (b) potential difference across the capacitor (c) energy of the capacitor
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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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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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How does the fringe width, in Young’s double-slit experiment, change when the distance of separation between the slits and screen is doubled?
The fringe width is β = λD/d If D (distance between slits and screen) is doubled, then fringe width will be doubled.
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