Light Intensity: Is it Decreasing at 1/r2?

[hiltac]

Hello,
If we consider a source of light (in a point x), is it wright to say that the intensity decreases in 1/r² ?

Thank you !

 

[mfb]

If r is the distance to point x, it is right. Note that there are no exactly point-like sources of light, so for real sources this is only an approximation.

 

[DaveC426913]

Does this apply to any light? Including, say, a laser?

 

[mfb]

Very far away from the source, yes, as you are always limited by diffraction. For a laser pointer (or all visible light lasers with a similar beam diameter), it becomes a good approximation after several hundred meters.

This assumes no absorption or other elements (like lenses) in the path, of course.

 

[sardar]

Yes, it is correct to say that the intensity of light decreases in 1/r2 as distance from the source increases. This is known as the inverse square law and is a fundamental principle in physics. It states that the intensity of light, or any type of radiation, decreases in proportion to the square of the distance from the source. This means that if you double the distance from the source, the intensity decreases by a factor of four. This law applies to many natural phenomena, such as the brightness of stars and the strength of gravitational and electric fields.