I disagree.
Many substances show fluorescence under ULTRAVIOLET light, NOT microwaves. :)
The answer is A. voice uses a wider range of pitch and volume as compared to speaking
The question involves a ping-pong ball that is held submerged in a bucket by a string attached to the bottom of the bucket.
The answer is the tension of the string will increase. This is because making the water salty increases its density, and consequently, increases its buoyancy. This is why sea water is more buoyant than fresh water. Therefore the ping pong is pushed more upwards by the water when salt is added than initially. This gives the string more tension.
Answer:
Force on superball will be 
Explanation:
We have given mass of superball m = 52 gram = 0.052 kg
Velocity change from 20 m/sec downward to 14 m/sec upward
Let downward velocity is positive then upward velocity is negative
So downward velocity is + 20 m/sec and upward velocity is -14 m/sec
Time is given as 1800 sec
We know that acceleration is rate of change of velocity
So 
According to newton second law
Force = ma = 0.052×0.0188 