Answer:
Explanation:
Using Coulomb's Law we know that the electric field E at point
is:

where
is the Coulomb's Constant, q is the source charge, d is the distance between point and position of the source point charge, and
is the position of the source point charge.
Taking all this in consideration, the unit vector clearly is:

For our problem,
, as the charge is located at the origin.
So

and d will be the magnitude of 
Now, we can take the values for each point.
<h3>a.</h3>

and, the magnitude of the vector is



So, the unit vector is:



<h3>b.</h3>

and, the magnitude of the vector is



So, the unit vector is:



<h3>c.</h3>

and, the magnitude of the vector is



So, the unit vector is:



Answer:
Wave theory of light explains the phenomena of interference, diffraction, scattering, dispersion, polarisation etc. Complete solution: Around 1700, it was concluded by Newton that light was a group of particles. It was called corpuscular theory.
We apply the gravity calculation expressed in the formula: g=GM/r2
where G is the gravitational constant, m is the mass and r is the radius
r=√GM/g
(1) Radius = √6.674e-11*5.972e24/8 = 7058 kms Earth radius or surface of earth from center of earth= 6400 kmsSo r= 658 kms from surface of earth.
Gravity 8m/s2 will be at 658 kms from surface of earth.
(2) half gravity= 9.8/2= 4.9 m/s2 Radius=√6.674e-11*5.972e24/4.9 = 9019 kms Half Gravity will exist at 9019-6400= 2619 kms from surface of earth.