What happens to the intensity of light

cbse
electromagneticwaves

#1

What happens to the intensity of light from a bulb if the distance from the bulb is doubled? As a laser beam travels across the length of room, its intensity essentially remains constant.
What geometrical characteristic of LASER beam is responsible for the constant intensity which is missing in the case of light from the bulb?


#2

As the distance is doubled, the area of spherical region will become four times, so the intensity
case of laser it does not spread, so its intensity remains same. .
Geometrical characteristic of LASER beam which is responsible for the constant intensity are as following:
(i) Unidirection
(ii) Monochromatic
(iii) Coherent light
(iv) Highly collimated
These characteristic are missing in the case of light from the bulb.