Hi Lukesh karmore
   Your code have small mistake, i rectitfied the mistake please see the below code,
   you are calling the array is error, see below code how to call the array elements
   efa.setFilename(cv[0].Title);
   efa.setbody(cv[0].versionData);

trigger sendEmailToContactWhenfileIsCreated on ContentDocumentLink (after insert) {
   set<id> conDocId=new set<id>();
   for(contentDocumentLink cond:Trigger.new){
    if(cond.linkedEntityId!=null ){
        conDocId.add(cond.linkedEntityId);
   }
}
list<Messaging.SingleEmailMessage> emailList = new list<Messaging.SingleEmailMessage>();
    list<contact> conlist=[select id ,email from contact where id in:conDocId];
for(contentDocumentLink cond:Trigger.new){
    for(contact c:conlist){
        contentversion cv=[select title,versionData from contentversion where id=:cond.contentdocumentId ];
        Messaging.SingleEmailMessage semail = new Messaging.SingleEmailMessage();
        list<string> toaddress=new list<string>();
        toaddress.add(c.Email);
        semail.setToaddresses(toaddress);
        semail.setsubject('Email Attachment');
        semail.setPlaintextbody('This is first email attachment');
        semail.settargetobjectId(c.id);
        emailList.add(semail);
        Messaging.EmailFileAttachment efa=new Messaging.EmailFileAttachment();
        efa.setFilename(cv[0].Title);
        efa.setbody(cv[0].versionData);
        efa.setFileattachment(new  Messaging.EmailFileAttachment[]{efa});
    }
      }
      Messaging.sendEmail(emailList);
}