Final answer:
The camera on/off button in a video visit via a mobile app is usually located at the top of the screen.
Step-by-step explanation:
The camera on/off button in a video visit via a mobile app is typically located at the top of the screen. This placement allows the user easy access to the button during a call without obstructing their view. The button is usually represented by an icon that can be tapped to toggle the camera on or off.