If the intensity of radiation at distance D from the source is 40 Units, then the intensity at distance 2D will be:

Question

Question

Answer 1

Correct Answer: 10 units

Rationale:

The intensity of radiation follows the inverse square law, which states that the intensity is inversely proportional to the square of the distance from the source. Mathematically, it can be expressed as I ∝ 1/D², where I is the intensity and D is the distance.
If the intensity at distance D is 40 units, then at distance 2D, the intensity will be 1/(2²) of the original intensity. This means it will be 1/4 of the intensity at distance D.
Thus, the intensity at distance 2D will be 40 units / 4 = 10 units.

Explanation of Other Options:

30 units

Rationale: This option is incorrect because it does not consider the inverse square law. The intensity would not be this high at double the distance.

20 units

Rationale: This option is also incorrect because it only reduces the intensity by half, which does not align with the inverse square law. The reduction should be by a factor of four.

5 units

Rationale: This option is incorrect because it suggests a reduction greater than what the inverse square law would predict. The correct reduction is to 1/4 of the original intensity, not 1/8.

Conclusion:

Among the given options, the correct intensity at distance 2D is 10 units, as per the inverse square law of radiation. This law is crucial in understanding how radiation and similar phenomena decrease with increasing distance from the source.