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Wireless ad-hoc network is a set of independent mobile nodes that communicates through a wireless link. Due to open medium and lack of centralized authority, ad-hoc networks are susceptible to numerous routing attacks. A wormhole attack causes severe threat to ad hoc networks and disrupts the entire communication process. If the source node chooses the route which contains malicious node, then they have much high probability of packet dropping. In this paper, we propose Path Tracing (PT) algorithm for detection and prevention of wormhole attack as an extension of DSR protocol. The PT algorithm runs on each node in a path during the DSR route discovery process. It calculates per hop distance based on the RTT value and wormhole link using frequency appearance count. Every node in a path has to compute per hop distance of its neighbor with the previous per hop distance to identify the wormhole attack. The corresponding node detects the wormhole if per hop distance exceeds the maximum threshold range. In the routing process, the wormhole link participates in more number than the normal link. This factor is used to detect the wormhole link using a link frequent appearance count. A network simulator (NS-2) results prove that the proposal detects the wormhole attack more effectively.