Q1.
Find the duration of the solar day by finding a difference in time on two consecutive days as shown in Table 11.2.
Answer
The shortest shadow of the day marks the moment the Sun is highest in the sky, so the gap between two such moments on consecutive days is one solar day. Using the readings printed in Table 11.2:
22 March 2025 — shortest shadow at 12:20
23 March 2025 — shortest shadow at 12:20
Duration = 12:20 next day − 12:20 = 24 h 00 min
23 March 2025 — 12:20
24 March 2025 — 12:19
Duration = 24 h − 1 min = 23 h 59 min
23 March 2025 — shortest shadow at 12:20
Duration = 12:20 next day − 12:20 = 24 h 00 min
23 March 2025 — 12:20
24 March 2025 — 12:19
Duration = 24 h − 1 min = 23 h 59 min
Why it works: As the Sun climbs, the shadow of a vertical stick swings round and gets shorter; as the Sun sinks, the shadow lengthens again. The single shortest shadow of the day is therefore the Sun's highest point — local noon. Marking a dot every minute from 11:00 a.m. to 1:10 p.m. gives you that moment to within about a minute without any clock reading of the Sun itself.
Tip: Fix the stick truly vertical and choose flat ground, or the shortest dot will be in the wrong place. Do not look directly at the Sun to judge its height — read the shadow instead.