Question

On what principle does the Sun-dial work?

• A. Length of the shadow changes as the Sun moves across the sky throughout the day.
• B. Position of the shadow changes as the Sun moves across the sky throughout the day.
• C. Length of the shadow changes from season to season as the Sun changes its position with seasons.
• D. Position of the shadow changes from season to season as the Sun changes its position with seasons.

Answer 1

The correct option is B Position of the shadow changes as the Sun moves across the sky throughout the day.

Sundials work from the shadow movement of a fixed object based on varying positions of the Sun throughout the day. It tells the time of day by the apparent position of the Sun in the sky. It consists of a flat plate (the dial) and a gnomon, which casts a shadow onto the dial. As the Sun appears to move across the sky, the shadow aligns with different hour-lines, which are marked on the dial to indicate the time of the day.