$\lambda_1=\lambda_2$

$\therefore \frac{1}{\lambda_1}=\frac{1}{\lambda_2}$

$\therefore\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right) \times Z_1^2=R\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right) \times Z_2^2$

$\therefore\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right) \times 1^2=\left(\frac{1}{2^2}-\frac{1}{4^2}\right) \times 2^2$

$\therefore \frac{1}{n_1^2}-\frac{1}{n_2^2}=\frac{1}{1}-\frac{1}{4}=\frac{1}{1}-\frac{1}{2^2}$

$\therefore n_1=1, n_2=2$