0 Simple light activated alarm using transistor

When there is light through the LDR, the circuit oscillates and a sound is generated to the speaker. First on the circuit on the dark and adjust potentiometer until the circuit will stop oscillating or no sounds is heard to the speaker.

schematic diagram

Part List :
R1 - 33 kilo ohms 1/4W
R2 - LDR (resistance from several ohms to Mega ohms)
R3 - 39 kilo ohms 1/4W
R4 - 33 ohms 1/4W
POT1 - 100 kilo ohms potentiometer (higher value the better)
Q1, Q2 - 2N2222 or similar NPN transistor
C1, C2 - 47nF capacitor
SPK - 8 ohms speaker
Bat - 9V battery