Question

If you are using high beams, you must switch to low when you are within ____ feet of the vehicle you are following?

1) 50
2) 100
3) 150
4) 200

Answer 1

When following a vehicle, you should switch from high beams to low beams when you are within 10.6 meters of the vehicle you are following.

Step-by-step explanation:

To determine the distance at which you must switch from high beams to low beams when following a vehicle, you need to consider the maximum distance at which the eye can resolve two headlights. The limit to the eye's acuity is related to diffraction by the pupil. Given that the two headlights of a car are 1.3 m apart, the maximum distance at which the eye can resolve them can be calculated using the formula:

Maximum distance = (Wavelength * Pupil Diameter) / (Angle between two just-resolvable points)

Using the average wavelength of light (550 nm) and a pupil diameter of 0.4 cm, we can find the angle between two just-resolvable points and then calculate the maximum distance as:

Maximum distance = (550 nm * 0.4 cm) / (angle)

The angle between two just-resolvable points for a 3.00-mm-diameter pupil is 6.18 arcminutes. Substituting this value into the formula gives:

Maximum distance = (550 nm * 0.4 cm) / (6.18 arcminutes)

Converting arcminutes to radians and simplifying the expression, we find that the maximum distance is approximately 10.6 m. Therefore, when you are within 10.6 m of the vehicle you are following, you should switch from high beams to low beams.