Physics
A standing wave occurs when

The amplitude of a wave exceeds its wavelength
Two waves overlap
The speed of the wave is zero or near zero
A wave reflects upon itself

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

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

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Physics
It is dangerous to observe Solar eclipse with naked eyes because

Cosmic rays reach eyes more during the eclipse
All radiations from sun initiate chemical reactions in eyes
Ultraviolet radiations from Sun burn our retina
Infrared radiations from sun burn our retina

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