Radiation Frequency and Penetration Depth ``` Name: Fowzy Status: student Grade: other Country: Germany Date: Winter 2012-2013 ``` Question: Why is it that high intensity laser radiation can have a higher penetration depth in a medium than low intensity radiation of the same wavelength? Why can it, on the other hand, have a high intensity laser have a lower penetration depth than a low intensity laser of the same wavelength in biological tissue? Replies: Hi Fowzy, Thanks for the question. Light penetration through a material generally follows an exponential decay law. The intensity of light that makes it through a distance "x" in a material is given by the following equation: I = A*exp(-B*x). I is the intensity of light that penetrates a distance x into the material. A is the intensity of light incident on the material. B is called the linear absorption coefficient. B tells you how much the material absorbs light. If B is larger, then more light is absorbed. So, if the intensity of light incident on a material is higher, the A value is higher and thus the penetration depth is larger. As mentioned in the first paragraph, the penetration depth depends on the B value. The B value depends on the wavelength of used. This explanation is my answer to your last question. I hope this helps. Please let me know if you have any more questions. Thanks Jeff Grell Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs