Tomatoes will ripen after being picked if exposed to light. What wavelength of light causes them to ripen? Is it visible light or does it have to be UV?
Are you talking about ripening picked green tomatoes?
This might be too Humble-Opiniony but here goes:
I think it comes down less to light and more to the tomatoes’ maturity.
I was always taught to wrap green tomatoes in newspaper and ripen them in a dark place. I was also taught that while you can ripen a green tomato without a star (that star-shape on the bottom of the tomato) it will not be as mature, meaty and flavorful as a tomato which does have the star.
FWIW, I had to pick a bunch of green tomatoes a few weeks ago and ripened them under a kitchen halogen light. Didn’t do the newspaper thing.
The larger ‘star’ ones have been pretty darn good.
The others were just okay.
Tomatoes don’t need light to ripen, they need ethylene gas. Here’s a gardener’s guide to ripening tomatoes and a detailed look at ethylene in tomato ripening.
I ripen my tomatoes in a paper bag, in a dark corner of the basement, and add an apple to each bag to supply the ethylene.