Intensities of an ordinary light and laser light
The intensity (I) of a wave is the energy per unit time flowing through a unit normal area. The light from an ordinary light source spreads out uniformly in all directions and forms spherical wavefronts around it.If you look at a 100 watt lamp filament from a distance of 30 cm, the power entering your eye is less than a watt.In case of a laser light energy is emitted in small region of space and in a small wavelength range and hence is said to be of great intensity as shown below. If you look directly along the beam from the laser (we should never do), then the power in the laser would enter your eye. Thus, even a 1 watt laser would appear many thousand times more intense that 100 watt ordinary lamp. For certain lasers, the intensity is so enormous that a power of 10^{15} watt can be concentrated into an area of 1 sqcm.