Final answer:
Sunlight is reflected more when horizontally polarized light bounces backward than forward, and sunglasses with vertical axes filter out this form of glare. Total internal reflection occurs when light meets an interface at an angle greater than the critical angle and is reflected entirely back into the denser medium.
Step-by-step explanation:
Sunlight is reflected when more of the light striking an object bounces backward than forward. This occurs because light can be considered as an electromagnetic wave that can be polarized. For instance, when unpolarized sunlight strikes a surface, the vertically polarized component of the light is preferentially refracted, leaving the reflected light more horizontally polarized. A mnemonic to remember this is to visualize polarization as arrows: vertical polarization, like an arrow sticking perpendicular to the surface, is less likely to be reflected, whereas horizontal polarization, like an arrow bouncing on its side, is more likely to be reflected. Sunglasses with vertical axes are designed to block this horizontally polarized light, which includes a lot of the glare from reflective surfaces, such as water or roads.
Moreover, total internal reflection is another interesting phenomenon where if light strikes the interface between two media at an angle greater than the critical angle, and the second medium has a lower index of refraction, all light gets reflected back into the first medium.
Learn more about Light Reflection