I know many sisters who make Du’a by playing a taped a Du’a made by an Imam. Is it correct for one to raise his hand and say ‘Ameen’ as the Imam makes the Du’a?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Saying ‘Ameen’ is in reality a supplication, because the meaning of Ameen is “O Allah do that or respond to this call”.

Therefore, if someone listens to a supplication directly from a person or from a tape and says ‘Ameen’, it is as if he made the supplication to Allah to accept and respond to that call which is mentioned, and a Mu’min is making the Du’a in reality, and if it is confirmed that saying ‘Ameen’ is a Du’a, therefore raising the hands when a supplication is made is an etiquette of Du’a. 

In principle it is a Sunnah to raise one’s hands when a Du’a is made, except in case when there is an evidence, that forbids raising hands in Du’a like when the Imam raises his hands during Jumu’a Khutba.

In a Hadith: “Allah is generous and shy, and is shy (not to reward a person who raises his hands) to turn back the hands raised for His Bounty without something (reward)”. [Reported by Ahmad]

Allah knows best.