Two strings with circular cross section and made of same material, are stretched to have same amount of tension. A transverse wave is then made to pass through both the strings. The velocity of the wave in the first string having the radius of cross section \( R \) is \( v_1 \), and that in the other string having radius of cross section \( R/2 \) is \( v_2 \). Then \( \frac{v_2}{v_1} = \)
