Question

mixing salt ,sugar and detergent powder in separate beaker of water and observing whether a laser beam is seen in them ​

Answer 1

Salt : If the salt is pure without any impurities than it would form a homogeneous mixture and laser light would be seen clearly.  

Sugar : Everything would be same as in the case of salt except for some minute changes like change in intensity of the beam but it would unnoticeable with naked eyes.  

Detergent powder : Detergent powder forms a colloid when mixed with water. This colloid is also uneven so laser light would be faint and its intensity would also change while moving the laser pointer.  

Hope it helps