A camera lens has an aperture of diameter 4cm. At what distance could it resolve the headlights of a car?
A camera lens has an aperture of diameter 4cm. At what distance could it resolve the headlights of a car that are 2.4m apart?
The wavelength of the light is 608nm.
The headlights of the car form single slit interference as they pass through the camera lens.
The light from each headlight spreads out into a smear.
The generally accepted resolution is
sin(theta) = x/L = 1.33 lambda / d
Now as the car headlight is white light then there are multiple colours.
If you take a value of around 6.08 * 10 ^ -7 as a reasonable figure then
L = xd / (1.33 lamdba)
= 2.4 * 0.04 /(1.33 * 6.08 * 10 ^ -7)
or about 119 km
Note that 4 cm is an ENORMOUS camera lens so this is why the resolution is so good.
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