A wheel initially at rest is subjected to a uniform angular acceleration about its axis. In the first \( 2 \, \text{s} \) it rotates through an angle \( \theta_1 \) and in the next \( 2 \, \text{s} \) it rotates through an angle \( \theta_2 \). The ratio \( \frac{\theta_2}{\theta_1} \) is ______________ .
