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 "Expansion" of Light
Name: Clay
Status: student
Age: N/A
Location: N/A
Country: N/A
Date: N/A


Question:
My question is why does light expand? Why does light get dimmer the further away it is from the source of the light?



Replies:
Clay,

For the purpose of your question, light acts like a wave. (because it acts like a wave, we can use the concept of throwing a large rock into a smooth pond to describe it)

If you throw a large rock into a smooth pond, the waves it creates will expand outwards. Because the wavefront is constantly increasing in size, and it's not receiving any additional energy, the energy in the wave gets spread over a larger and larger area, thus making the wave itself much smaller in height as it goes.

In other words, you went a long ways towards answering your own question. Light grows dimmer the further you are from it, because it is expanding. If you were to try this with a laser, which expands far less, than the amount it dims over distance would also decrease.

Ryan Belscamper



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