Question-
Explain "Lasers can get trapped in a waterfall" in detail in about 120 words.
Please provide only experts answer , please don't provide any web link or certified answer...

Yes. This is due to a phenomenon called total internal reflection  which occurs when light is travelling through a dense material and hits a boundary of a less dense material, for instance from water to air. If the critical angle is shallow enough, the light will reflect, and even if your water spout curves the light from the laser will travel down it. This is exactly how fibre optic cables work.