Answer:
Step-by-step explanation:
In a sonometer , expression for speed of wave produced can be given as follows .
v =

v is velocity , T is tension in wire , m is density per unit length .
Here v is inversely proportional to square root of m . So if m becomes m / 4
velocity changes as follows .
velocity =

=

= 2v
velocity becomes two times . Hence to make velocity two times , mass per unit length has to be changed to one fourth value , keeping tension constant .