Question

a person takes concentrated solution of salt.after some time he starts vomiting.whuch phenomenon is responsible for this?

Answer 1

Although our bodies can normalize sodium and chloride  concentrations to an extent, dealing with extremely high concentrations of salt in the blood is challenging. That's because a cell's membrane is semipermeable -- although sodium, chloride and other substances may not be able to easily diffuse in and out of the cell, water can. 
When the salt concentration is higher on the outside of our cells than on the inside, water moves from the inside to the outside of the cells to correct the imbalance. The attempt to equalize the concentrations of matter on both sides of a semipermeable membrane is called osmosis.

If you're consuming salt  water, the results of osmosis are spectacularly disastrous. Remember the salinity of  concentrated salt water is almost four times that of our bodily fluids. If gone unchecked, the net transfer of water from the inside of your cells to the outside will cause the cells to shrink considerably -- and shrinkage is never good

Answer 2

Concentration salt solution is a hypertonic solution (water concentration lower as compared to the cell) therefore it causes exosmosis. The outward movement of water from the cell results in irritation and excessive dehydration. This results in reverse movements and hence, vomiting.