$(1)$.The alpha $(\alpha)$ anomer of $D$-glucose has a specific rotation of $+112$ degrees in water.

$(2)$.The beta ( $\beta$ ) anomer of $D$-glucose has a specific rotation of $+19$ degrees. $(18.7$ actually, but rounding up to $19)$.

And when either anomer is dissolved in water, the value of the specific rotation changes over time eventually reaching the same value of $+52^{\circ}$.

The specific rotation of $\alpha$-D-glucopyranose decreases from $+112^{\circ}$ to

$+52^{\circ}$.

The specific rotation of $\beta$-D-glucopyranose increases from $+19^{\circ}$ to

$+52^{\circ}$.This behaviour is called mutarotation