BH1750FVI is a high presion lux sensor with IIC interface.You can react to the illuminate measured.

1. IIC interface
2. Approximates Human eye Response
3. Temperature range: -30 to 80 *C
4. Dynamic range (Lux): 1 to 655351 Lux

The lux (symbol: lx) is the SI unit of illuminance and luminous emittance, measuring luminous flux per unit area.It is equal to one lumen per square metre.

#include <Wire.h>
 
#define ADDR 0b0100011
 
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  Wire.begin();     
  Wire.beginTransmission(ADDR);
  Wire.write(0b00000001);
  Wire.endTransmission();
 
}
 
void loop() {
  // put your main code here, to run repeatedly: 
  int val = 0;
 
  // reset
  Wire.beginTransmission(ADDR);
  Wire.write(0b00000111);
  Wire.endTransmission();
 
  delay(100);
 
 
 
  Wire.beginTransmission(ADDR);
  Wire.write(0b00100000);
  Wire.endTransmission();
 
  // typical read delay 120ms
  delay(120);
 
  Wire.requestFrom(ADDR, 2); // 2byte every time
 
  for (val=0; Wire.available()>=1; ) {
    char c = Wire.read();
    //Serial.println(c, HEX);
    val = (val << 8) + (c & 0xFF);
  }
 
  val = val / 1.2;
  Serial.print("lx: ");
  Serial.println(val); 
 
  Serial.println("OK");
  digitalWrite(13, HIGH);
  delay(100);   
}

BH1750FVI-datasheet