How is a flashlight both luminous and nonluminous at the same time?
At first light it DOES sound a bit confusing.
First, the definition of the term 'NON-LUMINOUS'; 'Not capable of PRODUCING light but can be capable of REFLECTING light from another source'.
For instance, our MOON is NON-LUMINOUS as it REFLECTS light from the Sun. The SUN is LUMINOUS as it produces light that is REFLECTED off the surface of the moon. And so, LUMINOUS means capable of PRODUCING light.
Now closely examine your flashlight.
The BATTERIES produce electrical energy which is transferred to the BULB which emits light, thus LUMINOUS. The tiny little BULB emits quite a lot of light for its small size. However, the bulb is contained within a concave silvered cone which REFLECTS,(NON-LUMINOUS) gathers and channels the emitted light from the BULB (LUMINOUS) into a BEAM which ILLUMINATES whatever you are pointing the flashlight at.
Our cameras would be just paperweights if there were no NON-LUMINOUS surfaces for the light to REFLECT off of, back into the camera lens, onto the 'plate' thus etching the image. For example, take a photograph in the dark without the flash and what do you get. No LUMINOUS, no NON-LUMINOUS.
And so there we have LUMINOUS and NON-LUMINOUS, ILLUMINATING our lives. Enjoy! :) Read More At : Power On Board High Intensity Discharge Spotlight...