can u solve this (difference between 50Hz & 60 Hz)

This is easy - It is exactly 10Hz.

Advantages of 60Hz over 50Hz:

• less noticeable flicker in some kinds of lighting
• slightly smaller inductors and capacitors
• higher RPM for a given motor design

Advantages of 50Hz over 60Hz

• timing precision is a little easier
• because it is nearby (perhaps).....
• calculations all have a multiple of 5 in the answer....(easier on the slide ruler)

I'm reaching as far as I can....but this is really something of historical perspective. I can't say that I know what the historians were thinking, but I think there was some concern given to making a reliable clock in the thought process.

To paraphrase (if not quote) Mark Twain, "History does not repeat itself, but sometimes it rhymes".

Well, if you're in a country that has 50 Hz power it's an advantage to use appliances that are designed for 50 Hz, and it's a disadvantage to use appliances designed for 60 Hz.

If you're in a country that has 60 Hz power it's an advantage to use appliances that are designed for 60 Hz, and it's a disadvantage to use appliances designed for 50 Hz.

There isn't a global standard for low-voltage power supply. As national networks were developed they did so largely on the basis of not knowing or caring what the other countries were doing, to a greater extent, so the frequency difference is historical, as is the voltage difference.

Even where countries use the same frequency, e.g. France and Britain, there is always a phase difference between them, making conversion to DC and reconversion back to AC a requirement for inter-country power trading and load balancing arrangements.

The railways of Switzerland used 16²/₃Hz at one time....

P.S. Note that many power supply inlets for portable electronic equipment, such as some laptop computers, are arranged for multi-voltage, multi-frequency inlet, in an effort to overcome the problem of not knowing exactly where in the World its power will be drawn from.