In Unity, checking if an object is visible on the screen involves using the bounding box of the object and the camera's frustum. Here are the steps to accomplish this:

1. Get the object's bounds: The first step is to determine the bounding box of the object. This can be accomplished using the Bounds class in Unity. By getting the bounds of the object, you can determine the object's position, size, and whether it is within the camera's view.

2. Get the camera's frustum: The camera's frustum represents the portion of the game world that is visible within the camera's view. By obtaining the camera's frustum, you can determine the boundaries of what the camera can see.

3. Check for intersection: Once you have the object's bounds and the camera's frustum, you can check for intersection between the two. If the object's bounds intersect with the camera's frustum, then the object is visible on the screen. Unity provides various methods for checking intersection, such as Bounds.Intersects and GeometryUtility.TestPlanesAABB.

4. Consider occlusion culling: Unity provides occlusion culling to improve performance by hiding objects that are not visible to the camera. This means that even if an object's bounds intersect with the camera's frustum, it may still not be visible if it is occluded by other objects. You can use the occlusion culling data to determine if an object is actually visible to the camera.

By implementing these steps, you can effectively check if an object is visible in Unity. This can be useful for implementing game logic, such as triggering events when an object comes into view, or for optimizing performance by selectively rendering only visible objects. Keep in mind that checking for object visibility is an important aspect of game development, and mastering this technique can greatly enhance the overall user experience of your Unity game.