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

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

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Physics
A standing wave occurs when

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

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