Qstnid -Ii-6-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 - 22: Photometry - Neet-xii-physics

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NEET-XII-Physics

22: Photometry

with Solutions - page 2

Qstn# ii-6 Prvs-Qstn Next-Qstn

#6
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
(a) 40 lux
(b) 20 lux
(c) 10 lux
(d) 5 lux
digAnsr: a
Ans : Correct option
(a)
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.
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