A good quality LED should last for at least 25,000 hours, compared to 6–8,000 hours for a CFL and 1–2000 hours for an incandescent lamp.

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LEDs use much less energy to provide the same amount of light as other forms of lighting. One of the main reasons LEDs are so efficient is that most of their energy is used to solely create light, rather than creating light and heat, as less efficient forms of lighting do.

Yes, there are warm and cool white available. Warm white (yellowish light similar to an incandescent globe) is generally preferred in the main living areas and bedrooms, but cool white is usually acceptable in kitchen and bathroom areas.

If you are replacing 12V downlights, make sure the size and shape of the replacement LED lamp is compatible with your existing fitting.

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We present two figures of merit based on singular value decomposition, which can be used to assess the noise immunity of a complete Stokes polarimeter. These are used to optimize a polarimeter featuring a rotatable retarder and a fixed polarizer. A retardance of 132° (approximately three-eighths wave) and retarder orientation angles of ±51.7° and ±15.1° are found to be optimal when four measurements are used. Use of this retardance affords a factor-of-1.5 improvement in signal-to-noise ratio over systems employing a quarter-wave plate. A geometric means of visualizing the optimization process is discussed, and the advantages of the use of additional measurements are investigated. No advantage of using retarder orientation angles spaced uniformly through 360° is found over repeated measurements made at the four retarder orientation angles.

The Department of Climate Change, Energy, the Environment and Water's Light Bulb Saver app identifies the best light bulbs to replace incandescent and halogen bulbs, and can help you calculate your savings by switching light bulbs. It also provides tips about choosing the right lighting for each room in your house.

Although LEDs are relatively expensive to buy, good quality LEDS can last a long time – at least 25,000 hours. This makes them more cost-efficient than most other lighting types, as they don't need to be replaced as often.

We present two figures of merit based on singular value decomposition, which can be used to assess the noise immunity of a complete Stokes polarimeter. These are used to optimize a polarimeter featuring a rotatable retarder and a fixed polarizer. A retardance of 132° (approximately three-eighths wave) and retarder orientation angles of ±51.7° and ±15.1° are found to be optimal when four measurements are used. Use of this retardance affords a factor-of-1.5 improvement in signal-to-noise ratio over systems employing a quarter-wave plate. A geometric means of visualizing the optimization process is discussed, and the advantages of the use of additional measurements are investigated. No advantage of using retarder orientation angles spaced uniformly through 360° is found over repeated measurements made at the four retarder orientation angles.