int relay = 7;
int ldr = 8;

void setup() {
  pinMode(relay, OUTPUT);
  pinMode(ldr, INPUT);
  Serial.begin(9600);
}

void loop() {
  int val = digitalRead(ldr);
  Serial.println(val);
  if(val == 1){
    digitalWrite(relay, HIGH);
    delay(500);
    digitalWrite(relay, LOW);
    delay(500);
  }
}