When drivers traveling at night encounter a bright light from the vehicle behind them shining in their eyes, many will flip a tab on the underside of the rearview mirror to deflect the light up toward the ceiling of the car. The silvered surface of the mirror reflects approximately 85–90% of the incident light on the mirror, which is now directed toward the ceiling. The remaining 10–15% of the light is reflected by the front of the glass on the mirror. The mirror is wedge-shaped, thicker at the top than at the bottom. Thus the front surface is angled downward to allow the much smaller amount of light to be reflected into the driver’s eyes.