Test: Rotation and Revolution - Class 6 MCQ

The Earth rotates on its axis from west to east. This rotation causes the cycle of day and night as different parts of the Earth are alternately exposed to sunlight. Interestingly, this rotation is in a counter-clockwise direction when viewed from above the North Pole.

The Earth's axis is inclined at an angle of 23 degrees 20 minutes away from a line drawn perpendicular to the plane of its orbit around the Sun. This tilt is responsible for the changing seasons experienced on Earth as different parts receive varying amounts of sunlight throughout the year.

The correct answer is Option C: Circle of Illumination. This line is known as the circle of illumination, which is the boundary separating the illuminated half of the Earth from the dark half. It is the division that marks the transition between day and night on Earth.

Due to the Earth's rotation from west to east, observers on Earth perceive the Sun's movement in the sky as rising in the east and setting in the west. This daily cycle of the Sun's apparent motion is a direct result of the Earth's rotation on its axis, causing the Sun to appear to move across the sky from east to west.

The Earth always tilts in the same direction due to the principle of conservation of angular momentum. This means that once the Earth's axis is tilted in a particular direction, it tends to remain that way unless acted upon by an external force. This consistent tilt is what leads to the predictable changes in seasons.

The correct answer is Option C: West to East. Due to the Earth's rotation from west to east, the Sun appears to rise in the east and set in the west. This movement of the Sun across the sky is a result of the Earth's rotation on its axis.

The correct answer is Option D: Solar Illumination. Solar illumination refers to the process where the part of the Earth receiving light from the Sun experiences daylight. This phenomenon occurs as the Earth rotates on its axis, causing different regions to be exposed to sunlight at different times.

The varying day and night lengths on Earth throughout the year are primarily caused by Earth's axial tilt and its position around the Sun. This tilt, combined with Earth's revolution around the Sun, results in different angles at which sunlight reaches different regions of the Earth, leading to the changing lengths of day and night. This phenomenon is essential for the occurrence of seasons on our planet.

The changes in seasons on Earth can be explained by two astronomical events called equinox and solstice. Equinox, meaning 'equal nights,' occurs twice a year when day and night are approximately of equal length. Solstice, meaning 'Sun standing still,' happens twice a year as well and marks the longest and shortest days of the year. These events are crucial in understanding the transitions between seasons.

During the Summer Solstice, the North Pole is tilted towards the Sun, and the Sun's rays fall directly on the Tropic of Cancer. This positioning of the Earth leads to summer in the Northern Hemisphere. The Summer Solstice marks the longest day in the Northern Hemisphere with longer days and shorter nights. This phenomenon results in regions between the Arctic Circle and the North Pole receiving sunlight 24 hours a day for a few months, as the Sun never sets. Conversely, during this time, it is winter in the Southern Hemisphere, where nights are longer than the days, and the region between the Antarctic Circle and the South Pole experiences darkness for a few months without seeing the Sun.

The primary reason for the opposite seasons experienced in the two hemispheres of Earth lies in Earth's axial tilt. As Earth orbits the Sun, the tilt of its axis causes different hemispheres to receive varying amounts of sunlight at different times of the year. This discrepancy in sunlight exposure leads to the opposite seasons experienced in the Northern and Southern Hemispheres, showcasing the significance of Earth's axial tilt in shaping global climate patterns.

Days and nights are always of equal duration throughout the year only at the Equator due to Earth's axial tilt. The Equator experiences this phenomenon because it is positioned perpendicular to the Earth's axis of rotation, resulting in the Sun being directly overhead at noon throughout the year. This alignment minimizes the variations in day length caused by the tilt of Earth's axis, leading to consistent day and night durations at the Equator.

The Winter Solstice occurs when the Sun's rays fall vertically on the Tropic of Capricorn, with the South Pole tilted towards the Sun. This astronomical event signifies winter in the Northern Hemisphere, where the days are shorter and the nights are longer. During this period, regions between the Arctic Circle and the North Pole experience 24 hours of darkness for several months as the Sun remains unseen. Simultaneously, the Southern Hemisphere enjoys summer as the vertical rays of the Sun focus on the Tropic of Capricorn, resulting in longer days and shorter nights. Notably, 22 December is the longest day in the Southern Hemisphere during the Winter Solstice.

During the Winter Solstice, days are shorter in the Northern Hemisphere and longer in the Southern Hemisphere. This is a result of the South Pole being tilted towards the Sun during this period, causing the Southern Hemisphere to receive more direct sunlight and experience longer days. In contrast, the Northern Hemisphere receives less direct sunlight due to the tilt of the Earth away from the Sun, leading to shorter days and longer nights. This difference in daylight duration between the two hemispheres during the Winter Solstice is a key characteristic of this astronomical event.

The term 'Equinox' originates from Latin and signifies 'equal nights'. This term is derived from the Latin words "aequus" meaning equal and "nox" meaning night. During an equinox, day and night are approximately equal in length all over the world. This phenomenon occurs twice a year, marking the onset of spring and autumn.