Final answer:
The lens of a simple digital camera must be moved further from the sensor to focus on a closer object, going from a building 1 km away to a person 2.0 m away. In the case of many modern devices like smartphones, this is accomplished digitally rather than mechanically.
Step-by-step explanation:
When focusing a camera lens from a distant object to a close one, the lens must be moved in a direction that increases the distance between the lens and the camera sensor or film. In the case of changing focus from a building 1 km away to a person 2.0 m away, the lens must be moved closer to the sensor. This is because as the object distance decreases, the image distance (from lens to sensor) must increase to maintain focus, according to the lens formula №1/f = №1/u + №1/v, where f is the focal length, u is the object distance, and v is the image distance.
In a simple digital camera with a 4.3 mm focal length, originally focused on a building 1 km away, the lens is almost at its minimum distance from the sensor because the object is so far away. To focus on something 2.0 m away, which is much closer, the lens would need to be moved further from the sensor. However, it's important to note that in devices like smartphones, lenses and sensors are often fixed, and focusing is achieved digitally rather than by moving the lens.