The expression for transient photocurrent due to light pulse of arbitrary intensity has been derived in the presence of trapping and detrapping. The pulse duration is assumed to be short compared to the transit time and the analytic solutions are obtained for ``weak'' trapping case alone. Transcendental equations involving transit time and injected charge density have been solved numerically and the solutions are displayed graphically. In various limiting cases our expressions reduce to previously reported results. Analysis presented in this article may be useful in obtaining trapping parameters from experimental data.