What Are Polarized Lenses

Polarized lenses are transparent pieces of material, usually glass or plastic, that block certain types of light waves. Sunglasses and camera lenses are often polarized to reduce glare from surfaces, such as light reflecting off a lake or the hood of a car. Somewhat like the way Venetian blinds control the amount of sunlight passing through a window, polarization blocks as much as 50% of the light passing through a lens. The person looking through the lens can still see clearly in most cases, but it reduces the brightness and glare of light.

How They Work

When light bounces off of a surface, its waves tend to be strongest in a particular direction — usually horizontally, vertically, or diagonally. This is called polarization. Sunlight bouncing off a surface like water, a road, or metal will usually reflect horizontally, striking the viewer's eyes intensely and creating glare. Most polarized lenses in glasses are laminated with tiny vertical stripes that only allow vertically angled light to enter the wearer's eyes. Glare is eliminated because the horizontal light waves cannot bypass the vertical filter.

Lenses can be polarized to different degrees and in different ways. Most inexpensive polarized sunglasses have a thin film applied on one side of the lens. Many higher quality lenses have film laminated between two layers of lens material, preventing it from being scratched or rubbed off. In addition, the more dense the film is, the more polarization it provides. 

In most cases, polarized sunglasses don't look any different from regular sunglasses. While denser films tend to be darker, the color of a lens does not determine how much polarization it provides. A very dark pair of sunglasses with a light film will not block more glare than a lighter shade of glasses with a denser film. The color of the lens is also variable; although they cannot be made clear, polarized lenses can be made in gray, brown, green, or other colors.

Uses

Drivers, fisherman, and photographers were some of the first to use polarized lenses. Reducing glare can ease the eye strain drivers feel from long hours on the road. Fishermen can often see under the surface of water using the lenses, which helps them to see fish or other objects. Photographers use polarizing filters on camera lenses to enrich the images they capture by giving them more contrast, and to increase the range of effects they can produce.

Using horizontally and vertically polarized lenses together makes one type of three-dimensional (3-D) movies possible. Two images are projected onto a 3-D movie screen: one is polarized vertically and one horizontally. The lenses of the glasses that moviegoers wear are also polarized, one vertically and the other horizontally, so the user sees one image in one eye, and the second, slightly different image in the other. The brain is able to combine both of these images in a way that produces a realistic sense of depth.

Limitations

Polarized glasses do not provide universal protection from glare. If the wearer tilts his or her head past 45° or so, more of the horizontal light can enter and cause bright spots. In addition, these lenses do not usually work with snow glare because snow tends to reflect light equally in all directions, rather than the mostly horizontal reflection off of liquid water. It is strongly recommended that downhill skiers in particular not wear polarized sunglasses; ice does reflect horizontally, and these glasses can make dangerous icy spots less visible.

Because the polarizing stripes reduce the amount of light entering the eye, these lenses should not be used at night or in other situations where clear lenses are required. It is not possible to make such lenses truly clear; even those with low levels of polarization have a slightly gray hue. Some people find that looking through the lenses for too long a period of time can cause headaches and eye strain.

Polarized lenses can cause distortions in the way wearers see liquid crystal displays (LCDs), rendering some cell phone screens, clocks, and other displays unreadable. The texture of laminated or heat-treated glass, like a windshield, can be made more prominent by looking at it through a polarized lens, making the glass difficult to see through. Pilots should not use polarized glasses because they can make flight instruments difficult to read and other objects in the sky — including other airplanes — less visible.

Is It a Good Idea to Buy a Refurbished Mobile Phone

Is it a good idea to buy a refurbished mobile phone? It all depends. A refurbished mobile phone is one that has been returned to the factory from a cell phone company and rebuilt, usually to new specifications. Sometimes, a favorite model will no longer be manufactured new, but a customer can get a refurbished one.

A refurbished mobile phone should, in all respects, work exactly as a new phone. This is probably more likely to be the case when the refurbished mobile phone does not have many complex features, such as a camera, personal digital assistant and Bluetooth® capabilities. Cell phone customers routinely upgrade their mobile phones every couple of years or so, and the old ones have to go somewhere. Some are discarded, if they are no longer compatible with the cellular system, but many are sent back to the factory to be refurbished. This is also the case for phones that malfunction.

Whether buying a refurbished mobile phone is a good idea depends greatly on the manufacturer. Reputable makers usually produce a good product, but this may not be the case with "off" brands. A consumer should also always ask his or her cellular service provider if they have many refurbished phones returned for malfunction. Sometimes, the manufacturer will provide a warranty of some description, but the consumer should insist on one from the service provider. 

The question of getting a refurbished mobile phone may be crucial for someone who needs a phone at a moment's notice and cannot afford to risk having a refurbished mobile phone malfunction. On the flip side of that coin are elderly customers who have a good phone that they like. Many elderly customers don't want to have to learn how to use their phones all over again, and if a refurbished mobile phone in their preferred model is available, they may want one.

Price is another consideration. No customer should be asked to pay top dollar for a refurbished mobile phone. This is not fair. Even if a phone has many features, if it is refurbished, the customer should not have to pay what she would for a new phone. However, cellular service providers are aware of this, and they often offer a refurbished mobile phone as one of the free models for upgrade or for signing a service contract.

The main things a customer needs to consider when thinking about a refurbished mobile phone, then, are quality, warranty and price. If these are resolved to his satisfaction, then buying a refurbished mobile phone may be a sensible purchase.

What is an Unlocked Phone

An unlocked phone is essentially a phone that can be used with any SIM card from any network. Most cell phone companies install special “locking” software on their phones that prevents the phones from being used with any other network’s SIM card. However, there are ways to unlock a cell phone so that it can be used with any network.

One of the ways that cell phone companies attract new customers is to offer free or inexpensive phones when the customer signs a contract. In addition to charging a high termination fee if the customer cancels their phone line before the contract is up, cell phone companies protect themselves by locking all of the phones they sell to their network. This keeps them from losing money on customers who would buy a phone for a good deal from their company, then activate it with another network for a better rate.

Cell phone companies are able to do this because every modern cell phone has a tiny card in it called a SIM card. The SIM card is what identifies a cell phone as a certain phone number. In other words, a cell phone user can move their SIM card from one phone to another and still keep the same number. In addition, the SIM card is coded with the network’s identification information.

A locked phone essentially has software that prevents it from working with a SIM card that has any other carrier’s information coded into it. Unlocking a cell phone therefore enables the phone’s owner to leave one cell phone company for another. With an unlocked phone, a person can use whichever cell phone company is offering the best rate or the highest quality services.

Another advantage is that an unlocked phone is worth more money. Many sellers on eBay and elsewhere sell cellular phones. Since an unlocked phone appeals to a wider audience, instead of only those with a certain carrier, it is often worth the minimal expense to unlock the phone.

Unlocking a phone can be done online for very little money, usually under twenty U.S. dollars. Some phones require a special code to unlock them, which can be purchased online. Other phones can be unlocked by downloading software online and hooking the phone up to the computer. Unlocking a phone is generally not difficult, and since an unlocked phone gives users more options, the time and money it takes is usually considered worthwhile.