What happens to the absorbance at the analytical wavelength

Suppose that in the reaction Q R –> P only the product P is colored.What happens to the absorbance at the analytical wavelength for P of the mixture as the reaction progresses?Suppose you do an experiment involving this reaction in which Q is present in large excess of R. If this reaction is first order with respect to R would the graph of ln A for P versus time be straight line? Explain.