Relation Between Lens Length And Imager Size

I was using the calculator to learn the interrelationships between 'subject distance from camera', 'width' and AoV. Keeping everything constant, I changed the imager size from 1/3" to 1" and this changed the focal length. I don't understand how the imager size is related to the focal length.

It would be great if someone could explain this to me.

Thanks.

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**** * **** ** *** ********* *****, ***** ***** *** cross-section ** * **** *** *** ***** ***** ******* *** lens, **** *** *********** ***** (***** *** *** ***** *****), and **** **** ** *** ***** ****** (*** **** ****).

** ** *** *** **** **** ** * *" ***** sensor, *** *** ****** **** ** * */*" ***** ****** (it's ********* *** ** *****), *** *** *** *** *** smaller ****** ***** ** ******* **** ** *** ******* ***** from *** ****.

***'* ****** **** ******* ******* * ***** **:* ****** ***** (imager **** *** ****** ** ******* ** ** **** ***** resolution, ********* ***** ******* *** ******* *** **** ***** **********).

*** ******* ****** ***** *** **** *** **** ** *** image **** *** ** *** ****** **** ** *** ****** imager, ** ** **** * **** ******. **, ** *** the **** ***** ***** ** **** **** *** **** ****** that *** ****** ****** ****, *** ***** **** ** **** in.

** *** **** *** *** ***** ******** ********, *** ****** the ****** ****, *** **** **** ** ****** *** ****/***** length ** *** *** **** ****** *****.

******* *** **** ******** *** ******** ****** **** ***** ****** the *****/***.

*** ** **** ** **** *****/***** *****.

** *****,

****** **** **** *** *** ***********. ** ***** ******** *****.

*****, *** *** ****** ***** ** ** ******* *** ***** length? **** **** ** ****?

******* ** ****** ****** *** *** *** ** ****** *** change *** ***** ******. *** * **** ***** ********* **** 1/3" ** *" *** *** *** ******* ************* *** ***** length *** *** ****.

** ****,

****** *** **** *****. *** ***** ****** ******* **** * forced *** *** ** ** ********.

*'** ******** * ******** ** *** ************ *** **** *************.

** ******* ** ** ******* ********, * ***** *****'* ***** makes ******** *****.

****, ** *** ***** *** *** ** ** ******** *** change *** ****** ****, *** ***** ****** ***** ** ****** as ****.

**** ** * ********* **** * ****** ****** ******** * wider ***, *** ****** *****. ** **** *** **** *** imager **** ****** (*/*" ** *"), *** **** ** ********** by ****** *** ***** ****** **** ****** ** *** **** to **** *** **** ***.

** ****,

****** *** **** *****. *** ***** ****** ******* **** * forced *** *** ** ** ********.

*'** ******** * ******** ** *** ************ *** **** *************.

** ******* ** ** ******* ********, * ***** *****'* ***** makes ******** *****.

***** ***********, *****.

* ***** **** ********* **** *********:

...** *** *** **** ***** ***** ** **** **** *** [bigger] ****** **** *** [*******] ****** ****, *** ***** **** to **** **.

**** **** *** ** ******* *********. **'* **** *** **** put ***** **** */*" ******* ** ***'* *********.

@*****, **** *** *** *** "****** *** *** ** ** constant", **** **** **** **** *** ***** **** *** *** was *** ** **** *** */*" ******, **** ******* ** to *", *** **** ******* *** *** ** **** ** was ******, ***** ** **** ******* *** ***** ******?