int Led = 5;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(Led, OUTPUT);
}

void loop() {
 int LDR = analogRead(4);

 Serial.println(LDR);

if (LDR < 500 )
  digitalWrite(Led, HIGH);
else
digitalWrite( Led, LOW);

  delay(1000); // this speeds up the simulation
}