Question

1)Why would an LCD display on calculators or electronic wristwatches appear completely black when viewed through polarized sunglasses? How could one read the display without removing the sunglasses?

2)Why might it be beneficial for a photographer to have a polarizing filter for their camera when taking pictures outdoors?

3)What does the vertical polarization axis of polarized sunglasses indicate about the direction of polarization of light bouncing off a horizontal surface, such as a wet road or lake surface? Hint: The purpose of polarized sunglasses is to reduce glare without blocking out all light.

Answer 1

The structure of your LCD display (in a calculator or watch) is like a sandwich. You have a polarizer (Pol.1) a sheet of liquid crystal and a second polarizer (Pol.2).

The two polarisers are crossed so no light passes through, but the liquid crystal has the property of "twisting" light (rotate the Electric field; have a look to "elliptically polarized light") so that through Pol. 2 passes light (your display looks grey not black).
When you "activate" the liquid crystal (through one of the electric connections) you change the properties of it (at a particular position) so that now it doesn't twist light anymore. The light (horizontally polarized, for example) passes through without changes and gets blocked by crossed polarizer, Pol. 2.

When you look at your display (showing 1 for example) you see grey (light the was twisted and passes vertically polarized through Pol. 2) and the number, formed by "blocked" light.

If you wear polarized glasses it is possible that the axis of polarization of them is crossed with respect to the one transmitted by the lcd (around the number 1). So you'll see black for number 1 and black for the display, i.e., all black!

2)

They Protect Your Lens

The most affordable types of lens filters are those that are clear and simply used for protection. These are great for protecting the front lens element during normal shooting situations, as the clear glass does not affect your images in any way. Protective lens filters eliminate the possibility of scratches, cracks, and dust accumulating on the surface of your lens.

They Can Correct or Enhance Colors

There are certain types of photography filters that can alter or boost the colors in your images. Some have the ability to correct the color temperature of a scene, while others can enhance color and contrast for a more vibrant image.

They Help Ensure Accurate Exposure

When working with particularly difficult lighting conditions, filters are a great option for achieving even and accurate exposure across your entire image. They do this by blocking some of the light that enters the lens (in varying degrees). These are particularly helpful when shooting outdoors during daytime, particularly when using fast shutter speeds may not be enough to avoid overexposure.

They Add Impact to Your Images

Camera filters can help improve your images in various ways—they’re useful for increasing contrast in an image, creating more vivid colors, eliminating glare and distracting reflections from water and glassy surfaces, and more. But they can also be used to add a little oomph to an otherwise lackluster shot by adding some interesting effects, like multi-point “stars” on light sources or softened edges.

3)

When a bundle of light hits a flat surface, it becomes polarized, or is reflected horizontally. The bundle becomes concentrated and is blinding anyone observing it. This is referred to as blinding glare.

These reflections can be uniform, which is light reflected from a smooth service. Uniform reflections would be light reflected off the road, or off a car’s bumper or back window. They can also be non-uniform, which is light reflected from an uneven surface. An example of this would be light reflected off running water or a patch of ice on the road.

No matter what the case, the desired result is to filter out the distracting reflected light and provide a clear viewing experience for the wearer

Most of the glare that causes you to wear sunglasses comes from horizontal surfaces, such as water or a highway. When light strikes a surface, the reflected waves are polarized to match the angle of that surface. So, a highly reflective horizontal surface, such as a lake, will produce a lot of horizontally polarized light. Therefore, the polarized lenses in sunglasses are fixed at an angle that only allows vertically polarized light to enter. You can see this for yourself by putting on a pair of polarized sunglasses and looking at a horizontal reflective surface, like the hood of a car. Slowly tilt your head to the right or left. You will notice that the glare off the surface brightens as you adjust the angle of your view.