IR sensor controlling an electro magnet

Hi,

I need help with a STEM project for my daughter.

we want control an electro magnet using an IR sensor.

the electro magnet will hold up a sliding door until the beam is broken, the the door will release and fall.

it would have to be portable and run from a battery pack.

the electro magnet can be small, it won't have to hold much weight.

the sensor would need a range of less than 4 inches.

I am a novice, and really don't know where to begin.

please, any help would be great.

thanks.