You see the sun about 2 minutes before it actually rises, and 2 minutes after it actually sets — atmospheric refraction again.
The atmosphere bends sunlight around the curve of the Earth — you see the Sun ~2 minutes before it actually crosses the horizon.
'Actual sunrise' means the moment the Sun genuinely crosses the horizon. But you see it earlier than that, because the atmosphere bends the Sun's light around the curve of the Earth slightly — like a very gentle, gradual lens — letting the light reach your eyes even while the Sun is technically still below the horizon.
The same thing happens in reverse at sunset: you keep seeing the Sun for a couple of minutes after it has actually dropped below the horizon, because its light is still being bent up and over to reach you.
This bending is strongest near the horizon (where light travels through the most atmosphere) and gets weaker as the Sun rises higher. That's also why the Sun's disc looks slightly flattened at sunrise and sunset — the bottom edge is refracted upward more than the top edge, squashing the visible shape.
Key exam points
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Atmospheric Refraction: Advance Sunrise and Delayed Sunset — Class 10 Physics · CBSE Class 10 Physics