int ir=4;
int led=5;
void setup() {
  // put your setup code here, to run once:
pinMode(led,OUTPUT);
pinMode(ir, INPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
if(digitalRead(ir)==LOW)
{
  digitalWrite(led,HIGH);
}
else
{
  digitalWrite(led, LOW);
}
delay(20);
}