When a smartphone shifts focus from a distant mountain range to a nearby face
PHYSICS · Single correct · CBSE · Physics · Light — Reflection and Refraction · Light — Reflection and Refraction
Problem
When a smartphone shifts focus from a distant mountain range to a nearby face, the tiny lens moves relative to the fixed image sensor. Which statement best describes the required motion and the underlying reason?
(a) The lens must move slightly closer to the sensor because a nearer object forms its image at a shorter distance from the lens.
(b) The lens must move slightly farther from the sensor because a closer object requires a longer image distance to remain in focus.
(c) The lens must move slightly farther from the sensor because the focal length of the lens decreases for nearby objects.
(d) The lens does not need to move; the focal length is fixed, so focus is unchanged.