I am going to measure the concentration of cr by using UV spetrophotometer.
I want to know what is the maximum wave length of potassium dichromate to figure the calibration curve of it.

What is potassium dichromate maximum wavelength using UV specrophotometer?

It really depends on your matrix (if you can, make a scan on your spectrophotometer) - but try 257 nm.

Maximum wave length for 470 nanometer