"Obscura" is LATIN for DARK. Therefore a Room Obscura is a Dark Room.
This is an activity that engages all of my students. Truly it is like being inside a camera. This was a favorite END of YEAR activity for my students.
This was a common method for artists long, long ago to assist them in creating drawings and paintings. These can be created in boxes, tiny houses, or in your classroom! Luckily you may have a window that will have a nice view, but any view can work. You will need a surface parallel to the window in order to see the image. I just used the opposite wall (in my case it was a dry erase board). This was so popular at our school that other teachers, custodians and adults made their way to my room at the end of the day to relax in a dark room, talking softly watching the world go by.
You will be creating a hole (Lens) for the image to pass into your room. The small the hole, the sharper the image. Consider when you try to focus, often you squint.... a tiny hole helps narrow the focus, and sharpen the image.
WHY this work: Light travels in a straight line, this is a property called rectilinear propagation of light.