Why does time slow down for objects moving near light speed? Explain with light‑clock. (Conceptual Important)

Answer: In a light‑clock, a photon bounces between mirrors. At rest it travels vertical distance d per tick. If moving sideways fast, an observer sees a longer diagonal path but light speed must remain c for all. Longer distance at same speed means more time per tick, so moving clocks run slow (time dilation).