Which photon energy could be absorbed by a hydrogen atom that is in the n=2 state?

The differences between  a compression wave and a transverse wave?

If a balloon is taken outside on a very cold day, what will occur?

In a simplified model of the human eye, the aqueous and vitreous humors and the lens all have a refractive index of 1.40, and all the refraction occurs at the cornea, whose vertex is 2.60 cm from the retina. what should be the radius of curvature of the cornea such that the image of an object 40.0 cm from the cornea’s vertex is focused on the retina?