Considering only the magnitudes, which of the following quantities...

According to Cauchy's formula, the refractive index of a material is given by $\mu = A + \dfrac{B}{\lambda^2}$.

As the wavelength $\lambda$ increases, the refractive index $\mu$ decreases.

From the lens maker's formula, the focal length $f$ is given by $\dfrac{1}{f} = (\mu - 1)$\left(\dfrac{1}{R_1} - \dfrac{1}{R_2}\right).

The power of a lens is defined as $P =$\dfrac{1}{f}.

Since $\mu$ decreases with an increase in $\lambda$, the term $(\mu - 1)$ decreases. This implies that the magnitude of \dfrac{1}{f} decreases, and consequently, the magnitude of the focal length $f$ increases.

Therefore, the magnitude of the focal length of both a converging lens and a diverging lens increases as the wavelength is increased. The magnitude of the power of both lenses decreases.