int photoPin = A0; 
int redLedPin = 9;
int greenLedPin = 10;

float fixedResistor = 10000.0;

int dt = 1000;  

void setup() {
  Serial.begin(9600);        
  pinMode(photoPin, INPUT);
  pinMode(redLedPin , OUTPUT);
  pinMode(greenLedPin , OUTPUT);
}

void loop() {
int photoValue = analogRead(photoPin);

 // Conversion of analog Value which is between 0 to 1023 into analog voltage

float photoResistance = (fixedResistor * (1023.0 - photoValue)) / photoValue;
float brightnessLevel = map(photoResistance , 0 , 10000,0,255);

if(photoValue > 250){
  digitalWrite(greenLedPin , HIGH);
  digitalWrite(redLedPin , LOW);
}

else{
   digitalWrite( redLedPin , HIGH);
  digitalWrite(greenLedPin , LOW);
}

Serial.print("Photo Resistor Value = ");
Serial.println(photoValue);
Serial.print(",");
Serial.print("Resistance = ");
Serial.print(photoResistance);
Serial.println(", Brightness Level = ");
Serial.println(brightnessLevel);
delay(dt);
}