A light sensor is an input device that measures light levels. Your BBC micro:bit uses the LEDs to sense the levels of light and lets you program your micro:bit as a light sensor.
:class: important
Full details can be found at the **[BBC micro:bit MicroPython light documentation](https://microbit-micropython.readthedocs.io/en/latest/display.html?highlight=light#microbit.display.read_light_level)**.
The micro:bit uses the display’s LEDs in reverse-bias mode to sense the amount of light falling on the display.
Returns an integer between 0 and 255 representing the light level, with larger meaning more light.
For example:
:linenos:
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- **line 5** → creates an infinite loop, since the condition (`True`) will never be `False`.
- **line 6** → checks whether button A has been pressed
- **line 7** → takes the current light reading and stores it in the light_level variable
- **line 8** → waits for 100 milliseconds
- **line 9** → scrolls the light level across the display
- **line 10** → makes the display blank
- **line 11** → waits half a second
- **line 12** → turns on the centre pixel in the display
- **line 13** → waits half a second
- Create a program that samples light levels using the micro:bit's light sensor every two seconds. It should displays messages based on whether the light level has increased (↑) or decreased (↓).
- Create a program that measures the light level using the micro:bit's light sensor and activates all the LEDs on the micro:bit when the light level falls below a threshold of 100.