Answer
467 nm.
Work Step by Step
The wavelength in water is shorter by a factor of n than it is in air. Find the wavelength in air.
$$\lambda_w=\frac{\lambda_0 }{n_{water}}=526nm $$
$$\lambda_0=(1.333)(526nm)=701nm$$
The wavelength in benzene is shorter by a factor of n than it is in air. Find the wavelength in air.
$$\lambda_b=\frac{\lambda_0 }{n_{benzene}}=\frac{701nm }{1.501}
=467nm$$
