Step 1: Calculating wavelength of the waves.
Wave velocity is given by
\[
v = f\lambda.
\]
Substituting given values,
\[
\lambda = \frac{v}{f} = \frac{50}{200} = 0.25 \, \text{m}.
\]
Step 2: Distance between consecutive antinodes.
When two identical waves travel in opposite directions, a stationary wave is formed. The distance between two consecutive antinodes is
\[
\frac{\lambda}{2}.
\]
Step 3: Final calculation.
\[
\text{Distance} = \frac{0.25}{2} = 0.125 \, \text{m}.
\]
Step 4: Conclusion.
The distance between two consecutive antinodes is \(0.125 \, \text{m}\).