a-level physics (mc)

The equation used in explaining the bright fringes in Newton's Ring is,

2t = (m-1/2)w
where t is the thickness of the air-film at some distance from the centre of the lens
w is the wavelength of light used
m is an integer

when the lens is raised up, the thickness of air film t at a particular radius increases. The value at the left hand side increase, but w on the right hand side is fixed, hence m must be increased.

That is to say, at a certain distance from the lens centre, rings of the next higher order will move in to replace a ring of one-order lower. That means the rings are moving inward towards the centre.