You stand on a straight desert road at night and observe a vehicle approaching. This vehicle is equipped with two small headlights that are 0.681 m apart. At what distance, in kilometers, are you marginally able to discern that there are two headlights rather than a single light source

Complete Question

You stand on a straight desert road at night and observe a vehicle approaching. This vehicle is equipped with two small headlights that are 0.681 m apart. At what distance, in kilometres, are you marginally able to discern that there are two headlights rather than a single light source?Take the wavelength of the light to be 549 nm and your pupil diameter as 4.63 mm.  

The distance is  

Explanation:

From the question we are told that

    The is distance between the headlight is

   The wavelength is  

    The  pupil diameter is  

Generally, we can mathematically evaluate the resolution of the eye as

    substituting values

Now according to SOHCAHTOA rule  

Where z is  the distance at which the eye can discern the two head light

  given that the angle is very small

=>    

substituting values

=>  

=>    

d is the correct answer