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Late one night on a highway, a car speeds by you and fades into the distance. Un

ID: 1379040 • Letter: L

Question

Late one night on a highway, a car speeds by you and fades into the distance. Under these conditions the pupils of your eyes have diameters of about 7.3 mm. The taillights of this car are separated by a distance of1.0 m and emit red light (wavelength = 676 nm in vacuum). How far away from you is this car when its taillights appear to merge into a single spot of light because of the effects of diffraction? Late one night on a highway, a car speeds by you and fades into the distance. Under these conditions the pupils of your eyes have diameters of about 7.3 mm. The taillights of this car are separated by a distance of1.0 m and emit red light (wavelength = 676 nm in vacuum). How far away from you is this car when its taillights appear to merge into a single spot of light because of the effects of diffraction?

Explanation / Answer

From the Raleygh's criterion

?=1.22 L/D

?= 1.22 ((676E-9 m)/(7.3E-3m ))

?= 1.129x 10^-4 rad

from the diagrem angle can be expressed as
?= r/s

1.129x 10^-4 rad= (1.0 m)/(s )

s = 8857.39 m