- Why does the rubber on my flashlight smell smokey and how can I get rid of the odor?
You can try this: scrub it with baking soda, then let it sit, still covered in it for a day or so. Baking soda is great at absorbing odors, and should not damage it in any way. Just don't let any of it accidentally get into the battery compartment. If that doesn't do it, then it may just be the chemicals used in making the rubber itself, and you may just be stuck with it. Good luck.
- How can i find the focal length of the lens in my flashlight?
If you can take off the lens completely: remove lens. Hold it up and try to focus a distant light source on a wall. I usually use light coming in a window. Alternatively, try and focus a ceiling light on to the floor. As long as the source is a few metres away, this will give you a pretty good answer for the focal length.
- What is the purpose of a red lens and blue lens on a flashlight?
Red Light is used for prevserving night vision so your eyes won't have to readjust. A Blue Light makes it easier to spot fluids in tanks such as in a Windshield Wiper Fluid Reservoir. A Green Light helps with map reading better. Also a clear lens with indentations and flutes in it is used for spreading the light outwards and dimming it somewhat. On some flash lights including military flash lights these lens can be combined for suitable situations.