Answer:
12.6 cm
Explanation:
We can use the mirror equation to find the distance of the image from the mirror:

where here we have
f = 9.50 cm is the focal length
p = 39 cm is the distance of the object from the mirror
Solving the equation for q, we find:

Answer:
The electric potential at the surface of a charged conductor<u> is always such that the potential is zero at all points inside the conductor.</u>
Explanation:
Each point on the surface of a balanced charged conductor has the same electrical potential.
The surface on any charged conductor in electrostatic equilibrium is an equipotential surface. Since the electric field is equal to zero inside the conductor, the electric potential at any point inside and on the surface is equivalent to its value.
Answer:
Explanation:
Electric field due to a point charge Q at a point at distance d is given by the relation
E = 
Since Q1 and Q2 are of the same magnitude and distance , so they will create eletric field of same magnitude. Similarly field due to rest of the charges will also be same.
The charges are situated on the corners of a square in such a way that
equal charges of Q1 and Q3 are situated on the diametrically opposite corners of the square. Fields due to these two charges will be equal and opposite in direction. Therefore net field due to these two charges will be zero.
On the same ground, we can say that field due to Q2 and Q4 at the centre will be equal and opposite and therefore they will cancel out each other. Net field at the centre will be zero
Overall, net field due to all the four charges will be zero
The Electromagnetic and Visible Spectra. I believe..