Step 1: Understanding the Concept
\(T=2\pi\sqrt{\dfrac{m}{k_{eff}}}\).
For the same arrangement of four identical springs, \(k_{eff}\propto k\).
Step 2: New spring constant
Replacing k with \(2k\) doubles the effective spring constant: \(k_{eff,2}=2k_{eff,1}\).
Step 3: Ratio
\(\dfrac{T_1}{T_2}=\sqrt{\dfrac{k_{eff,2}}{k_{eff,1}}}=\sqrt{2}\)
So \(T_1:T_2=\sqrt{2}:1\).
Final Answer:
The ratio of time periods is root two to one.
\[ \boxed{\text{(C) }\sqrt{2}:1} \]