From your earlier studies of 'potential dividers' you should know that the position of the LDR within the potential divider will determine if the circuit is light or dark sensitive.

You should also know that using a Thyristor rather than a transistor would 'latch' the circuit and the lamp would then need to be turned off when dawn raised the light levels again !
Or you could use a 741 Op-Amp.

One final item that may be needed in the circuit could be a relay. Using this would allow the circuit for the lamp
itself to be separate from the lower powered circuit that did the sensing of the light levels