How far can a flashlight be seen?

[bobbagum]

Now in that link I see amateur radio operators transmitting light, and since light is an electromagnetic wave, would this be considered operating in unauthorized/licensed band? :naughty:

 

[AnAppleSnail]

Now in that link I see amateur radio operators transmitting light, and since light is an electromagnetic wave, would this be considered operating in unauthorized/licensed band? :naughty:

I think that the FCC has an unspoken exception for unlimited broadcast on the 400-790 THz band except where such interferes with the safety of transportation and emergency services. How's that for a new flashlight warning?

"This device has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These standards are designed to provide reasonable protection against harmful interference when these devices are operated in a commercial environment. These devices generate, use, and can radiate visible frequency energy and may cause harmful interference to visual operations unless used in accordance with this User's Guide. Operation of these devices outside confined areas is likely to cause harmful interference which will make the user responsible for the appropriate remedial action at his / her own expense."

 

[StarHalo]

I've always wondered how the size of reflector and/or lighting element affects the visibility

A smaller, more intense source of light focused into a compact beam is the key to throw; a bigger reflector is better, but the DEFT takes it a step further by using a large aspheric lens, so you get a super-tight "fat laser" beam.

unlimited broadcast on the 400-790 THz band

 

[Limey Johnson]

A bit off topic, but similar...this reminds me of a true story.

While standing in line at the grocery store, I was in front of two women arguing about how far the human eye can see. One girl said she can easily see a mountain range that's almost 100 miles from her relatives property.

The other girl swore she was full of ****, and that maybe could see 20 miles at the most.

This, unfortunately was a slow moving line, and when I had enough, I ended the argument with one question..."excuse me ladies...have either of you ever seen the moon?"

can't make this stuff up.

 

[StarHalo]

And on a clear night, you can see the Andromeda galaxy, 150,000,000,000,000,000,000 miles away

 

[Cataract]

hehe, it's not even about how far our eyes can see, it's about how far a sufficient amount of light can reach

 

[Kestrel]

How far can a flashlight be seen?

If Mrs. Kestrel last used it, it quite often can't be seen at all, particularly in the last place I had left it.