Alight ray travelling from diamond into air has an angle of
refraction of 56°. a piece of glass is then placed right next
to the diamond.
(a) how will the angle of refraction change?

The angle of refraction can be computed using Snell's Law: n1*sin θ1 = n2*sin  θ2, wherein n1 and n2 refer to the refractive index of mediums 1 and 2, respectively and  θ1 and  θ2 are the angles of refraction. The refractive index of air it is 1.00029 and for glass it's 1.52. Using the formula and the given values, the angle of reaction due to glass is 33.06 degrees.