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
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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
Explanation:
- This won't have any angular distribution, as the beam is parallel. And, in the end, the illuminance will remain the same.
- So in this case, it is going to be 40 lux.
- Angular distribution is nothing but the distribution in angle of the power of photons or particles originating from a nuclear or extra nuclear cycle, Relative to the path set experimentally.
Therefore the correct answer is Option (a) 40 lux
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The illuminance produced when it falls on a wall 4 m away is close to (a) 40 lux.
Explanation:
The illuminance is given by the formula:
Illuminance = (Luminous power)/(Area)
From question, we know that the light produced from torch is a parallel beam. So, the area of the beam does not change with the distance.
The power of the torch also remains the same which means luminous power remains the same.
Thus, the power of the illuminance at 2 m and 4 m is same.
Thus, illuminance produced when the wall is 4 m away is 40 lux.
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