#### Answer

$\lambda_1 = 2\lambda_0$
$f_1 = f_0$

#### Work Step by Step

We can write an expression for the initial conditions;
$\lambda_0 = \frac{v_0}{f_0}$
We know that the frequency does not change when a wave goes from one medium into a new medium. We can write an expression for the new conditions;
$\lambda_1 = \frac{v_1}{f_1}$
$\lambda_1 = \frac{2v_0}{f_0}$
$\lambda_1 = 2\lambda_0$