How your phone sensors work?

Sensors are everywhere in our day to day life. It's in your phone in your computer everywhere; from remote sensing satellites to the fire indicating sensors. So for us we need to first understand it how it works; before this I want you to give idea about how sensors are important. Let's take an example of self driving car AI can compute all the data and can take decision about the driving but without sensors it can not take data from outside world to function properly; you can say that sensors are the skin of AI.

Now sensors are build to understand physical information like heat, temperature, sun light, humidity, pressure in atmosphere etc; However they don't have any brain. In order to sense physical phenomenon they use receptors for example of silicon if I want to build a sensor which can sense whether light is on or off so I just have to put silicon if light is on then it will produce electric current which turn on the alarm or anything to send; by calculating the amount of current produce we can tell that how much visibility should be there. Computer just compute those data and tell this kinds of things.

Your cellphone has 10 sensors; your car has 400 but your body has none this is about change.

                                                                                         - Vinod Khosla

There are two kinds of sensors.

1. Active
2. Passive

1. Active

Active sensors emit waves or radiation which comes into the contact of surrounding and then comes back to the sensors. Computer compute the time it takes to arrive and angle then it produce Map of surrounding. for example RADAR.

2. Passive

Unlike active sensors; passive sensors never emits anything but they grab the radiation from the objects surrounding to extract useful data. In astro-science field scientists use this kind of method to detect black holes, cosmic background radiation. Cosmic background radiation has shown below.