The circuit seems to be a modification of this circuit
with only one LDR.
The circuit is not guaranteed to function, because the 741 is not rated to operate on 9 V.
Right. The datasheet
states under recommended operating conditions: supply voltage (min) +- 10 V.
In addition, assuming your specific chip would work from + 9 V, there is another limit, namely output voltage of the 741. The same datasheet tells us that the output voltage swing of the 741 is in worst case 3 V from the supply voltage, which in case 0f a single 9 V supply means the output swings between +3 V and + 6 V (assuming >= 10 kΩ load, which is given in this circuit). Adding 0.6 V base-emitter voltage of transistor Q1 means the voltage on the trigger pin 2 of the 555 timer ic would not go below 3.6 V (worst case, lower if ther output of the 741 is better than specified).
The trigger input (pin 2) of the 555 requires < 3 V when the 555 is operated from 9 V (datasheet
). As the input voltage to pin 2 of the 555 will under the above conditions not go below 3 V, the 555 will never be triggered.
as suggested by @AnalogKid
is a much better choice instead of the 741. Notethat these chips have different pinouts, you'll have to adapt the pin numbering when using anoter opamp instead of the 741.