An electric current produces a magnetic field because of
a.) magnetism
b.) the moving protons
c.) magnetic field
d.) induction

One day, after pulling down your window shade, you notice that sunlight is passing through a pinhole in the shade and making a small patch of light on the far wall. you see that the patch of light seems to be a circular diffraction pattern. it appears that the central maximum is about 1 cm across and you estimate that the distance from the window shade to the wall is about 3 m. what is (a) the average wavelength of sunlight? (b) the diameter of the pinhole?

Arock collection comes from which part of earth?

In positive numbers less than 1, the zeros between the decimal point and non zero are significant