Hi Sindhu,
I agree with the asnwer given above by Alessandro. The only thing I would like to add, according to your question, that the transfer function of this filter will be a well-known step-function. This function can be described by various polynomials. The higher the orders of this polynomials the closer this function will be to a step function. Please, see following links as examples:
https://www.andovercorp.com/products/bandpass-filters/standard/193-299nm/
https://www.finisar.com/sites/default/files/resources/white_paper_waveshaper_filter_bandwidth_definition.pdf