The "dolly zoom" is a very effective way to convey this imo.

https://filmschoolrejects.com/wp-content/uploads/2021/01/Jaw...

https://filmschoolrejects.com/wp-content/uploads/2021/01/Fel...

https://screenqueens.files.wordpress.com/2017/08/polt.gif

https://screen-queens.com/2017/08/24/how-the-dolly-zoom-chan...

There's also some rather neat series that play with perspective. Don't have any at hand but google:

https://photography.tutsplus.com/tutorials/exploring-how-foc...

https://static.wixstatic.com/media/7d67c8_1d09b657f6a04e6fb8...

The way I've always explained it to people as a photographer: your position with regard to the subject determines the perspective, which is the relationship between objects in the composition. Your choice of focal length determines what field of view/image area of that perspective that you want to capture.

And yes, to agree with a parent comment, this is something that zoom lenses have rotted the brains of many photographers on. People stand wherever is convenient and then zoom to fit the subjects, rather than thinking first about how they want the elements to be placed within the image. You should move to where the elements have the proper relationship, then figure out your field of view from there.

To use the Jaws example: if you want the tent in the frame, you need to be close and go wide. If you want to exclude the tent from the frame, you go farther away and zoom in. As a photographer, you need to make that decision about your composition first, and then choose the position that gives you that, and then select your field of view last.

It's hugely beneficial imo to work with a 3-lens kit or something similar (eg 28mm, 50mm, 105mm) for at least a little while, to really force you to think about what you want from a particular exposure/composition.

A useful implication of this: you get the exact same perspective from taking a picture with a wide angle lens and cropping it to your desired composition, as if you had taken the same photo with a long lens and not cropped it at all. You just get less resolution - so it's obviously desirable to use a longer lens if you have one - but the perspective is the same either way. Similarly - if your lens isn't wide enough, you can stitch together multiple exposures and it will be the same as if you had used a wider lens. Perspective is completely independent of focal length of the lens, it's purely a property that emerges from the relative positions of the subject and photographer. All the lens is doing is picking a "crop".

(to get really really tangential: this is one of the problems I have with "photojournalism" as a field of photography and photojournalism contests in particular, because it completely forbids things like cropping as somehow tampering with the essence of an image. But cropping is a natural part of composition, you do it with your lens even if you are not doing it in photoshop. The photographer (if they're good) chose to exclude the mother idly smoking a cig as she waits for the bus and compose the screaming baby in the carriage instead. Pretending like there is a "platonic truth" to an image because it "wasn't edited" despite being deliberately constructed by a photographer with an agenda (towards drama and impact, if nothing else) and editorial and artistic license is a microcosm of the way modern media feigns complete neutrality and unbiasedness by "just reporting facts" while completely ignoring the agendas of those who choose what facts are reported and the framing used. Anyway, those "photojournalism contests" should really be called "straight-out-of-camera" contests, and even then there is still processing happening. There is no platonic "right" way to process a RAW into a JPG, even if it's the camera doing it itself. But "straight-out-of-camera awards wouldn't be something that sounds important enough to give a bunch of money and adulation over :])