What is the force opposing gravity of earth or simply gravitational force?(We can use this to invent magic broomstick like in harry potter movies!!!..)

Gravity is the weakest force in nature but depends on the mass of the particles involved. If you use any other force (Any of the three other fundamental forces or the derivatives of them) it may be read more

Why the ray of light passing through optical center of a lens passes undeviated while when it passes through other points on the interface of the lens, it gets refracted?

Deviation is the change in direction of the ray while passing through the lens. The middle portion of the lens is comparatively flat and there is a point on the principal axis and inside the sphere read more

Why the ray of light passing through the centre of curvature of a concave mirror behave as normal while it doesn’t behave as normal when it passes through other points on the principal axis?

Remember that a concave mirror forms part of a hollow sphere.

Any line joining the centre of the sphere (the centre of curvature of the mirror) and any point read more