Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12

A Battery-operated Torch is Adjusted to Send an Almost Parallel Beam of Light. It Produces an Illuminancle of 40 Lux When the Light Falls on a Wall 2 M Away. - Physics

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A battery-operated torch is adjusted to send an almost parallel beam of light. It produces an illuminancle of 40 lux when the light falls on a wall 2 m away. The illuminance produced when it falls on a wall 4 m away is close to _________ .


  • 40 lux

  • 20 lux

  • 10 lux

  • 5 lux

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40 lux


Since the beam is parallel, it will have no angular spread. So the illuminance will remain same throughout. Therefore, in this case, it will be 40 lux.

Concept: Light Process and Photometry
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HC Verma Class 11, Class 12 Concepts of Physics Vol. 1
Chapter 22 Photometry
MCQ | Q 6 | Page 454

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