Answer:

Explanation:
The refractive index of a medium is a measure to know how much the speed of light within the medium is reduced. It can be calculated with the next equation:
(1)
Where:


The speed of light in the vacuum is approximately 300,000 km/s. In order to work with the same units let's do the proper conversion with the velocity of the medium:

Finally, replacing the data in (1):

Answer:
c.
Explanation:
We are given that
Acceleration due to gravity on the moon=
Acceleration due to gravity on the earth=

Net force due to am on an object on moon=
There is no friction and no drag force and there is no gravity involved
Then, the force acting on an object on earth=
(given)


Hence, option c is true.
Answer:
It’s called a conservative field.
Explanation:
I think it’s going to be the conservative field because in the question it talks about how it is able to become possible to define potential at a point in an electric field because electric field.
Answer:
Magnification, m = -0.42
Explanation:
It is given that,
Height of diamond ring, h = 1.5 cm
Object distance, u = -20 cm
Radius of curvature of concave mirror, R = 30 cm
Focal length of mirror, f = R/2 = -15 cm (focal length is negative for concave mirror)
Using mirror's formula :
, f = focal length of the mirror


v = -8.57 cm
The magnification of a mirror is given by,


m = -0.42
So, the magnification of the concave mirror is 0.42. Thew negative sign shows that the image is inverted.
We can use the law of conservation of energy to solve the problem.
The total mechanical energy of the system at any moment of the motion is:

where U is the potential energy and K the kinetic energy.
At the beginning of the motion, the ball starts from the ground so its altitude is h=0 and therefore its potential energy U is zero. So, the mechanical energy is just kinetic energy:

When the ball reaches the maximum altitude of its flight, it starts to go down again, so its speed at that moment is zero: v=0. So, its kinetic energy at the top is zero. So the total mechanical energy is just potential energy:

But the mechanical energy must be conserved, Ef=Ei, so we have

and so, the potential energy at the top of the flight is