Light is passed through a solution with a light path of 1 cm and the absorbance is recorded as 0.30. if light is passed through the same solution at the same wavelength and the light path is increased to 2 cm, the absorbance should be

Absorbance = 0.60
       
Absorbance should be double the original because the length is double. Beer-Lambert Law equation is A = eLC, where A is absorbance, e is extinction coefficient, L is length that the light is passing, and C is concentration of the solution. If all parameters are the same except for L (length of the light passing though) then it should change as the same factor, which in this case is 2, because 2cm/1cm = 2 time change in length.

That would be a working theory.