The plots of intensity against wavelength for three black bodies at temperatures $T_1$, $T_2$ and $T_3$ are as shown. The wavelengths are such that

From the given graph, the horizontal axis represents the wavelength $\lambda$.

Let $\lambda_1$, $\lambda_2$, and $\lambda_3$ be the wavelengths corresponding to the maximum intensity (the peaks of the curves) for the black bodies at temperatures $T_1$, $T_2$, and $T_3$ respectively.

By observing the positions of the peaks along the $\lambda$-axis:
The peak of the curve for $T_1$ is furthest to the left, meaning it corresponds to the smallest wavelength, so $\lambda_1$ is the minimum.
The peak of the curve for $T_3$ is in the middle, so $\lambda_3$ is greater than $\lambda_1$.
The peak of the curve for $T_2$ is furthest to the right, meaning it corresponds to the largest wavelength, so $\lambda_2$ is the maximum.

Therefore, the correct relationship between the wavelengths is:
$\lambda_1 < \lambda_3 < \lambda_2$

Answer: $\lambda_1 < \lambda_3 < \lambda_2$