(It is easy to see that the radius of the bright spot is of the same order of magnitude.) The experiment succeeds in a dark room of the length above mentioned, with a threepenny bit (supported by three threads) as obstacle, the origin of light being a small needle hole in a plate of tin, through which the sun's rays shine horizontally after reflection from an external mirror.
The customary unit of expenditure is the threepenny-bit or "tickey."
Threepenny bits there " \m we still made mistakes.
Threepenny loaves on the first Sunday in every month to the poor who attend the chapel.
Threepenny piece in my pudding.
How would you define threepenny? Add your definition here.