Physics
Answer
A solar eclipse occurs when the moon during its course of revolution passes between the sun and the earth and the three heavenly bodies position themselves in a straight line such that the moon fully or partially covers the sun, as viewed from some parts of the earth.
Since the light from the sun is blocked by the moon, the shadow of the moon falls on the earth and it becomes dark during the daytime. Solar eclipse occurs only on a new moon day.
The formation of solar eclipse is shown below :
