Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Infrared Radiation and Temperature
Name: Rey
Status: other
Age: N/A
Location: N/A
Country: N/A
Date: N/A


Question:
How does infrared radiation make your skin feel hotter?



Replies:
The skin absorbs infrared radiation by causing various molecules making up the surface of your skin vibrate more rapidly. This increase in the kinetic energy (the energy of motion) nerves sense as "heat". The details of the process are pretty complicated but that is the basic mechanism.

Vince Calder


Rey,

All radiation, including visible light and radio waves, carries energy. When radiation meets a material, such as skin, it can be absorbed, reflected, or it can pass through. Infrared radiation passes through the cells on your retina. This is why you cannot see it. Radio waves can pass through your entire body. Most visible light is reflected from a piece of white paper. Infrared radiation is ABSORBED by your skin.

When the radiation is absorbed, the energy enters your skin. This makes the molecules in your skin shake around more than usual. This is what a high temperature is. Another example of this effect is when you stand near a vent while the furnace is running. The vibrating molecules in the warm air cause your skin molecules to vibrate. This too makes your skin feel hotter. Absorbing energy can often cause temperature to increase.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College


Your skin might be considered as having about 3 layers: inner, middle, and outer. Each has a successively cooler temperature, due to body heat flowing outwards. As a way of measuring the magnitude of this outbound heat flow, the nerves in your skin very sensitively measure temperature difference between middle and inner layers. (The outer layer is too dead, tough, and dangerous to be worth investing with nerves.)

When infrared light shines on your skin, some is absorbed in the middle layer, making it slightly warmer than it would have been, or at least subtracting a little from the usual outwards heatflow.

Deeper in the body, starting with the inner layer, blood flow carries heat around more vigorously. If positioned any deeper, this nerves-measuring-temperature-gradients business would not work too well.

I wonder if it is possible for some heat-sources, some wavelengths of infrared, to warm up the inner layer more than the middle layer, resulting in a feeling of cool instead of warm? It would probably have to be temporary to work, a brief pulse of radiation.

Jim Swenson



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

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory