Why is the `C-O-H` bond angle in alcohols slightly less than the tetrahedral angle whereas the `C-O-C` bond angle in ether is slightly greater ?

Explanation

The C-0-H bond angle in alcohols is slightly less than the tetrahedral angle `(109.5^(@))` because of larger repulsions Letween the lone pairs of electrons. For example in methanol, C-O-H bond angle is `108.9^(@)`.
In ethers, the C-O-C bond angle is alightly greater than tetrahedral angle. For example in dimethyl ether, C-0-C bond angle is `111.^(@)`. The larger bond angle in ethers may be because of greater repulsions between bulkier alkyl groups as compared to one H in alcohols.