Thread: chairgun
View Single Post
Old 21st July 2015, 08:33 AM
Monty's Avatar
Monty Monty is offline
Senior Moment
Join Date: Aug 2013
Member of: Southampton Buccaneers, Basingstoke ARPC
Location: Southampton
Posts: 227
Default inverse square law

Originally Posted by blacklab View Post
would a 150 watt halogen lamp be enough to lite up the paper
But put it as close as you can without risk of shooting it. Light follows the inverse square law, if you double the distance from the subject the light reflected is quartered. if you have the light at 10cm away from the paper then move it to 20 cm the amount of light reflected (and therefore what you can see) is now only 0.25 as much and the scope picture will be much darker. If you move it 50cm away its 5 times further and the image will be almost black as the light reaching the target will be 0.04 times as bright so get your light source as close as possible.
ISP Airstream MK III No 15 which is a bit poorly at the moment and having a rest
AA Pro Sport + Ginb FT8 stock + Bushnell 4200 6-24x
EV2 MK1 + Leupold Comp 40x
Weihrauch HW100 KT laminate

SBFTC Competition Secretary
Reply With Quote