Physics
Railway tracks are banked on curves so that

No frictional force may be produced between the tracks and the wheels of the train
Necessary centrifugal force may be obtained from the horizontal component of the weight of the train
Necessary centripetal force may be obtained from the horizontal component of the weight of the train
The train may not fall down inwards

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Physics
An electron microscope gives higher magnification than an optical microscope, because :

The wavelength of electrons is smaller as compared to the wavelength of visible light
It uses more powerful lenses
The velocity of electron is smaller than that of visible light
The electrons have more energy than the light particles

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