So we can modify light outside of the visible spectrum via sophisticated lenses with the result being a new frequency inside the visible spectrum.
What I would like to do is different. I would like to explore (with my eyes) the edges of the visible spectrum i.e. red and violet. Ideally, I would love to have a light bulb, which emits light of any frequency required. That way I will make it red, and then decrease the frequency until it becomes invisible. That is, I am curious how sharp is the drop-off in our eyes' transfer function with frequency.
Trouble is, I don't have any laboratory equipment. All I have is an oscilloscope, breadboard and basic knowledge of controlling LEDs.
Is this feasible? I would expect a compromise solution as well, e.g. wait for a rainbow and look at it's edges.