Sundial Quiz By MS. Sadia Qamar

Explanation
A sundial is a device that tells time based on the position of the sun. To use a sundial, the most essential requirement is the presence of the sun. The sun's rays cast a shadow on the sundial, and by observing the position of the shadow, we can determine the time. Therefore, the correct answer is the sun. Clouds and water are not necessary for the functioning of a sundial as they can obstruct the sunlight and prevent accurate time measurement.

Explanation
The central stick in a sundial is called a gnomon. The gnomon is the part of the sundial that casts a shadow, allowing the time to be determined based on the position of the shadow. It is typically a straight, vertical stick that is aligned with the Earth's axis and is angled to correspond with the latitude of the location where the sundial is being used. The gnomon is an essential component of a sundial as it helps in measuring the passage of time based on the movement of the shadow it casts.

Explanation
A portable compass is built with a compass. A compass is a navigational instrument that uses the Earth's magnetic field to determine direction. It typically consists of a magnetized needle or dial that aligns with the Earth's magnetic North and South poles, allowing users to determine which way is North. Therefore, the correct answer is compass.

Explanation
During the 1300s, mechanical clocks were invented. This period marked a significant advancement in timekeeping technology, as mechanical clocks relied on intricate mechanisms and gears to accurately measure and display time. Prior to this, various forms of timekeeping devices such as sundials and water clocks were used, but they were not as precise or reliable as mechanical clocks. The invention of mechanical clocks in the 1300s revolutionized timekeeping and paved the way for the development of more sophisticated and accurate timepieces in the future.

Explanation
The size of the shadow is shortest at midday because the sun is directly overhead, causing the object to cast a shorter shadow. At sunrise and sunset, the angle of the sun is lower, resulting in longer shadows. During the night, there is no sunlight to cast any shadows.