The Shortlist...
How Is A One Way Mirror Made?
How Can You Tell Its A One Way Mirror?
Touch your fingernail on the mirror. If there is a gap between the surface and your nail, then it is a real mirror, if there is no gap in the mirror, it is a two way mirror.
Can Light Shine Through A One Way Mirror?
No light cannot shine through a one way mirror. A two way mirror can have light shine through it because of the way the light reflects.
Where Are Two Way Mirrors Used?
A lot of time two way mirrors are used in various law enforcement centers so that personnel can watch the interview to look for tells that the person is lying.
In some mental health settings they are used for observation and safety purposes.