Best location for a light bulb filament using a concave mirror?

[reganw]

Where is the best location for a light bulb filament to be placed in a spotlight, when using a concave mirror?

It makes the most sense to put it at the focal point of the mirror if you want parallel light beams but are you supposed to have parallel light beams when you use a spotlight? Or do you want the beams to diverge slightly so the light covers a larger area? I also read that in some slide projectors, the light bulb is placed at the center of curvature.. is this the same thing as radius of curvature? Or are they meaning focal point? I'm just a little unclear..

Thank you in advance for your help!

 

[Spinnor]

See:

http://www.saskschools.ca/curr_content/physics20/light/curv_app_lamps.htm

http://www.google.com/search?hl=en&...&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi

Some flashlights you can adjust the bulb for or aft of the focal point.

 

[PeterO]

Where is the best location for a light bulb filament to be placed in a spotlight, when using a concave mirror?

It makes the most sense to put it at the focal point of the mirror if you want parallel light beams but are you supposed to have parallel light beams when you use a spotlight? Or do you want the beams to diverge slightly so the light covers a larger area? I also read that in some slide projectors, the light bulb is placed at the center of curvature.. is this the same thing as radius of curvature? Or are they meaning focal point? I'm just a little unclear..

Thank you in advance for your help!

Don't forget that no light bulb is an actual point source of light, so while some point on the filament may be exactly at the focus, the rest of is will be slightly off, giving a certain amount of spread.

Peter

 

[reganw]

Don't forget that no light bulb is an actual point source of light, so while some point on the filament may be exactly at the focus, the rest of is will be slightly off, giving a certain amount of spread.

Peter

See:

http://www.saskschools.ca/curr_content/physics20/light/curv_app_lamps.htm

http://www.google.com/search?hl=en&...&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi

Some flashlights you can adjust the bulb for or aft of the focal point.

Okay, that's great, thank you to the both of you! I can put together a sufficient answer with all of that info. Thanks again.

 

[rwisz]

I would suggest placing the light bulb filament at the focal point of the concave mirror for optimal use in a spotlight. This will create parallel light beams that can cover a larger area. However, if you want to create a more focused beam, you can place the filament slightly closer to the mirror's surface. It is important to note that the center of curvature and the focal point are not necessarily the same thing. The center of curvature is the midpoint of the mirror's surface, while the focal point is the point where parallel light rays converge after being reflected by the mirror. In some cases, the center of curvature and the focal point may be very close to each other, but they are not interchangeable. It is always best to consult the manufacturer's instructions for specific placement guidelines for your particular spotlight.