LINK for REAL mode Experiment.
   • Smart street light using LDR and LED ...  

Working Principle:
1.When the torch is near the LDR (Bright light on LDR):
The LDR resistance decreases significantly (from several kilo-ohms to a few hundred ohms).
Since the LDR is connected between base and emitter, it creates a low-resistance path, diverting base current away from the transistor.
The transistor does not get enough base current, so it remains OFF.
No current flows from collector to emitter, so LED remains OFF.
2.When the torch is moved away (Darkness on LDR):
The LDR resistance increases (to several kilo-ohms or more).
The 10kΩ resistor pulls the base of the transistor HIGH, allowing base current to flow.
The transistor turns ON, allowing current to flow from collector to emitter.
This allows the LED to turn ON.
Conclusion:
Circuit functions as a dark-activated switch where the LED turns ON in the absence of light and turns OFF when exposed to bright light. This behavior is due to the LDR controlling the transistor’s base current.