A camera obscura is the predecessor of modern day cameras. It works by letting light in through a small pinhole and projects it onto a surface (e.g. a wall).
To build a room obscura we need to choose a room which gets plenty of sunlight. I chose my bedroom for this.
Next we need to identify all the sources of light and completely seal them. In my case I used garbage bags to cover my two windows.
I used packing tape instead of duct tape as it can tear off paint from the wood. However, this led to some light bleeding in from the edges. I fixed this using aluminum foil.
I experimented with three pinholes of various sizes.
After trapping out all the light I mounted my camera next to my pinhole and captured the image.
This was the best result I could get using a pinhole of 0.4 inches.
It is extremely important to perform this experiment on a sunny day, otherwise you will not get a clear image.
You should also experiment with different focal lengths, i.e. adjust the distance between your pinhole and the screen. This can produce a sharper image.