In scientific notation, we write a number so that it has single digit to the left of decimal sign and is multiplied by an integer power of 10.
Note that moving decimal p digits to right is equivalent to multiplying by 10^p and moving decimal q digits to left is equivalent to dividing by 10^q.
Hence, we should either divide the number by 10^p i.e. multiply by 10^(-p) (if moving decimal to right) or multiply the number by 10^q (if moving decimal to left).
In other words, it is written as axx10^n, where 1<=a<10 and n is an integer.
To write 0,00194 in scientific notation, we will have to move the decimal point three points to right, which literally means multiplying by 10^3.
Hence in scientific notation 0.00194=1.94xx10^(-3) (note that as we have moved decimal three points to right, we have multiplied by 10^3 and to compensate we have multiplied by 10^(-3).
