SQL & PL/SQL

Hi!

create table t1 (
  n number,
  v varchar2(2)
);

create table t2 (
  n number,
  v varchar2(2)
);

insert into t1 values (1, 'a1');
insert into t2 values (1, 'a1');
insert into t2 values (1, 'a2');
insert into t2 values (1, 'a3');
insert into t2 values (2, 'a1');
insert into t2 values (2, 'a2');
insert into t2 values (3, 'a1');
commit;

select * from t1      join t2 on t1.n=t2.n and rownum=1;

N V
- --
1 a1

select * from t1 LEFT join t2 on t1.n=t2.n and rownum=1;

N V
- --
1 a1
1 a1
1 a1

Why the second query returns 3 rows? ROWNUM seems to be ignored.
Explain me that, please. I'm now aware of some "inside things", probably.