Final answer:
Visual checks are crucial before changing lanes to cover areas not visible in mirrors, even when using a diverging rear-view mirror which provides a wider field of view but may alter the perception of distance and size of the objects.
Step-by-step explanation:
The reason for making visual checks to the left or right before changing lanes is because it covers areas not visible in mirrors. Rear-view mirrors on vehicles can only reflect so much of the area behind the vehicle due to their shape and position. While some mirrors use a diverging mirror, which can reflect a wider field of view than a flat mirror, they do not entirely eliminate blind spots. This is why drivers are encouraged to physically check over their shoulder to cover any areas that the mirrors can't cover. Diverging mirrors are often used because they allow drivers to see a broader area behind them, reducing blind spots and helping with awareness while driving, but their main disadvantage is that they make objects appear smaller and further away than they actually are, which can sometimes make it difficult to judge distance and speed of approaching vehicles accurately.