Homework Help: Could Paul Revere discern if there were one or two lanterns?

1. Apr 16, 2013

Plasmosis1

"one if by land and two if by sea" is the famous saying of Paul Revere when he was a certain distance away from a signal sent from the people of old North Church in Boston on the night of April 18, 1775. if the average human pupil has a diameter of 4mm at night and the lanterns had a predominant wavelength of 580 nm how far away (in miles) was Paul Revere when he received the signal about the approaching British on that fateful night? assume he was at a minimum distance of .5 m and neglect any other influences- including the shortening of the wavelength in his eye (which does not change the answer). could he actually discern if there were one or two lanterns? Show work for why or why not.

Useful equation: thetamin= 1.22*wavelength/diameter

I don't believe that there is enough information for this problem. You have two variables, distance from the lanterns and the angle created between the lanterns. Any help would be appreciated.

2. Apr 16, 2013

barryj

I think the equation gives the resolving power of the eye in radians. This comes out to be 1.76E-4 radians. I would think the lanterns would be 0.5 meters apart. Now you can determine how far away you can be to resolve the two lanterns., yes??

3. Apr 16, 2013

rude man

The problem's wording is terrible but I think you have the right approach to it nonetheless.

4. Apr 16, 2013

barryj

I think you have a similar question on this forum about can a spy satellite see a license plate.