void setup() {
// initialize digital pin 13 as an output.
pinMode(13, OUTPUT); // this is the blue led
pinMode(10, INPUT);  // this is the IR sensor's O/P

}

// the loop function runs over and over again forever
void loop() {
digitalWrite(13, HIGH); // first I give HIGH voltage to the blue LED

if(digitalRead(10) == LOW){  // when the voltage of the IR sensor decreases
digitalWrite(13, LOW); // the blue LED should switch off or have 0 Voltage
}

}