the large round one.
you hide behind stuff then keep doing it until he shrinks himself with the mirror
To finish Shrink Ray island, drive the toy truck to the school and avoid the Shrink Ray attack by Mr. Silva. Jump from the desk to the lab bench using the globe. Use the mirror to reflect the beam back on Silva, and you can restore yourself and CJ to normal size. (see the related questions for the complete solution)
There is a sticky note on the computer. It says my hero. Jump on bed see poster: her hero is Marie Curie. In the bathroom, when you turn on the hot water, the mirror will say a=4, i=1, 3=e. Go to the toilet, look at the newspaper. Go to computer, type it in. The password, btw, is M4r13Cur13.
If you mean the mirror in mhytology island, then you can travel with this.
aphrodite
Aphrodite.
go into the store, run right. pick up the mirror
Go to the store click on the mirror on the right and the woman will give it to you for free.
a lady at the beach has it she will ask you the gods and if you get it all right she will give you the mirror.
The broken mirror on Skullduggery Island is in the General Store. (At the upper right.)
A mirror can be used as a reflector to signal passing ships or airplanes. A mirror may be used to signal a ship or an airplane that you are on the island. Reflecting the sun's rays into the cockpit of an airplane might bring help.
go to the store and the lady will give you a fre mirror