Parallax error happens when the measurement of the length of an object is more/less than the actual length of an object. This is basically an error that happens due to the wrong positioning of the eye during measurement especially at an angle to that of the device markings.
A simple example-
Anyone reading a car’s speedometer directly from the driver’s seat will more or less get an accurate reading. That’s because the person will have a direct line of sight. On the other hand, a person who’s seated on the passenger seat will make a mistake in his/her readings. That’s because s/he’s seated at angle.
Parallax errors are common occurrences in school/college practical exams. In this article, we are going to discuss a few ways through which parallax error can be reduced in the best possible manner.
Orientation of eyes should be in a straight line
This is the most obvious of all precautionary measures that should be implemented to curb the parallax error in the best possible way:
Your eyes should be in a straight line directly above the marking on your device, be it a scale or a Vernier caliper etc. Like we said before, parallax error mainly happens because the object is viewed from an angle. This makes the measuring object appear at a different position than that of the actual position.
Place the measuring device on its edge
You should always place the device (the one you are using for measurement) on its edge such that it is level with that of the object being measured.
If the marking is below or above the object, it’ll magnify any sort of parallax error that’s caused by the line of sight being at an angle to that of the marking.
Use a fine-edged device
Try to use a device having finer edges. A wider edge is a part of the problem by allowing larger parallax error. The object will appear to be higher or lower with respect to that of the actual position.
Read the lower meniscus of liquid to get an accurate measurement
While measuring the level of any liquid in a graduated cylinder, you’ll have to take the reading of the lower meniscus (it’s the lower portion of the curved surface of the liquid).
This will give an accurate measurement avoiding parallax errors at the same time.
Take the average of readings
An average of multiple readings will more or less provide you with an accurate reading. You can ask your mates to take the same measurement. Record the readings. Make an average of the same and you’ll see the result will be much closer to that of the actual measurement.
Parallax error is a form of random error. Therefore, it can be curbed to a certain extent by taking readings at random and calculating the average of the same.