update opportunity when account updated

trigger CopyToOpportunity on Account (after insert, after update) {
    List<Opportunity> opportunityList = new List<Opportunity>();
    for(Account ac : Trigger.New) {
        for(Opportunity opp : [select Source__c from Opportunity where accountid = :ac.id]) {
            opp.Source__c = ac.Source__c;
            opportunityList.add(opp);
        }
    }
    update opportunityList;
}