Question Corner

Seeing double

QUESTION: My sister, who is quite short- sighted, pointed out that when she looks in a mirror, the image of a distant object looks just as out of focus as the actual object when viewed directly. Why is this?

ANSWER: The reason why the object is just as blurry to your short-sighted sister is because the light has to travel the distance to the mirror and then from the mirror to her eye. You are looking at the sum of the two distances, not at the mirror itself. A simple experiment to prove this is to get a small sticker and place it at eye level on the mirror. Note that looking at yourself, at an object behind you, and at the sticker on the mirror all require you to adjust the focus of your eyes accordingly. It appears as if the object behind you is actually behind the mirror, and exactly that same distance away from it.

Therefore the distance from the eye of the viewer equals the distance of the viewer from the mirror plus the distance of the object from the mirror.

Anybody checking their appearance in a mirror would do well to bear this principle in mind. It could save you from acute embarrassment.

Remember that you are looking at yourself from twice the distance to the mirror. If you want to check for blemishes make sure that you get closer. You'll be able to spot things that you wouldn't normally notice - New Scientist

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Verifying Adulteration

QUESTION: How to verify purity of honey

J.John Silas, Chennai

ANSWER: Honey is adulterated by way of adding jaggery syrup.To verify whether honey is pure, take a glass of waterand pour one tablespoon of honey in it. Gently shake the glass (note not to stir). If the honey completely dissolves in water it is adulterated. On the other hand if it stays as a mass, it is pure honey.

N.Nagasubramanian, Chennai

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Linear and non-linear editing

Question: What is non linear editing? How is it different from linear editing?

Ms. V. Revathi, Bangalore.

Answer: Linear editing systems and non-linear editing systems are used in video and film editing. In Linear editing systems, edits to be made in a linear fashion; i.e., in 1-2-3 sequence. One or more tapes containing the original footage are transferred (recorded) segment by segment onto a tape in a video recorder.

In the process, the original segments can be shortened and rearranged, bad shots can be removed, and audio and video effects can be added. The source machine(s) contain the original footage, and the edit recorder, which is controlled by an edit controller, is used to record the final edited master.

The person editing, uses an edit controller to shuttle tapes back and forth to find the beginning and ending points of each needed segment.

These reference points are then entered as either control track marks or time code numbers. The editor then turn things over to the edit controller, which uses the precise beginning and ending points that have been entered, to roll and cue the tapes and make each edit.

Non-linear editing is a little like working with a highly sophisticated word processor; it allows segments to be inserted, deleted and moved around at any point in the editing process. In non-linear editing the original video segments are digitised (they are not in digital form when they come out of the camera) and transferred to computer hard disks. The editing system can access them in any order, almost instantly.

During nonlinear editing a wide range of special effects can be added, including fades, dissolves, keyed-in words and scene-to- scene colour corrections. Many audio enhancements can also be added, including sound effects.

K. Kamalakannan, Doha, Qatar.

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This Week's Questions

Which device controls the automatic on and off of sodium and mercury vapour lamps used in street lights?

N.Senthil Kumar,Guindy

How does a simcard function in a cellphone?

B.Murugavel, Kanchipuram,T.N.

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