 
Phases

The Moon does not produce any light of its own; it only reflects light from the Sun. As the Moon moves around the Earth, we see different parts of the near side of the Moon illuminated by the Sun. This causes the changes in the shape of the Moon that we notice on a regular basis, called the phases of the Moon. 

As the Moon revolves around Earth, the illuminated portion of the near side of the Moon will change from fully lit to completely dark and back again. A full moon is the lunar phase seen when the whole of the Moon’s lit side is facing Earth. This phase happens when Earth is between the Moon and the Sun. About one week later, the Moon enters the quarter-moon phase. At this point, the Moon appears as a half-circle, since only half of the Moon’s lit surface is visible from Earth. When the Moon moves between Earth and the Sun, the side facing Earth is completely dark. This is called the new moon phase, and we do not usually see the Moon at this point. Before and after the quarter-moon phases are the gibbous and crescent phases. During the gibbous moon phase, the moon is more than half lit but not full. During the crescent moon phase, the moon is less than half lit and is seen as only a sliver or crescent shape. It takes about 29.5 days for the Moon to revolve around Earth and go through all the phases

Tides and eclipse

Tides are the regular rising and falling of Earth’s surface water in response to gravitational attraction from the Moon and Sun. The Moon’s gravity causes the oceans to bulge out in the direction of the Moon. In other words, the Moon’s gravity is pulling upwards on Earth’s water, producing a high tide. On the other side of the Earth, there is another high tide area, produced where the Moon’s pull is weakest. As the Earth rotates on its axis, the areas directly in line with the Moon will experience high tides. Each place on Earth experiences changes in the height of the water throughout the day as it changes from high tide to low tide. There are two high tides and two low tides each tidal day.

Spring tides occur at New Moon and Full Moon when the Sun, the Moon and the Earth are in line. Neap tides occur at First Quarter and Last Quarter, when the Sun, the Earth and the Moon are at right angles.

Eclipses occur when a large shadow travels across the surface of the Earth. When the new moon comes between the Earth and the Sun along the ecliptic, a solar eclipse is produced. When the Earth comes between the full moon and the Sun along the ecliptic, a lunar eclipse occurs.

Time and seasons

As Earth rotates, the side of Earth facing the Sun experiences daylight, and the opposite side (facing away from the Sun) experiences darkness or night time. Since the Earth completes one rotation in about 24 hours, this is the time it takes to complete one day-night cycle. As the Earth rotates, different places on Earth experience sunset and sunrise at a different time. The tilt on the Earth's axis causes day and night to be of different lengths in different parts of the world.

Seasons change as the Earth continues its revolution, causing the hemisphere tilted away from or towards the Sun to change accordingly. When it is winter in the Northern hemisphere, it is summer in the Southern hemisphere, and vice versa. The season depends on how much of the Earth's surface is covered by light rays, and at what angle they reach the Earth's surface. Head-on rays on a small area are strong and cause summer seasons. Slanting rays focusing on a large area are weaker and cause winter seasons.

 



Maths

How do the relative positions of Earth, the moon, and sun cause the phases, tides, and eclipses, and determine time on Earth?

Reduction = 3/4 of 64 = 64*(3/4) = 48 
Price of shirt in sale = 64-48 = £16 

English

The price of a shirt is usually £64 During a sale the prices in the shop are reduced by 3/4 How much is the shirt in the sale ?

Biology

How to use it

Physics

Specific heat capacity

When the new moon comes between the Earth and the Sun along the ecliptic, a solar eclipse is produced. When the Earth comes between the full moon and the Sun along the ecliptic, a lunar eclipse occurs.

- A full moon is the lunar phase seen when the whole of the Moon’s lit side is facing Earth. This phase happens when Earth is between the Moon and the Sun. 
- About one week later, the Moon enters the quarter-moon phase. At this point, the Moon appears as a half-circle, since only half of the Moon’s lit surface is visible from Earth. 
-When the Moon moves between Earth and the Sun, the side facing Earth is completely dark. This is called the new moon phase, and we do not usually see the Moon at this point. 
-The last Quarter Moon occurs the moment the opposite half of the Moon is illuminated compared to the First Quarter Moon. At first quarter and last quarter, the Moon lies perpendicular to a line between Earth and the Sun. 



What are the relative positions of the sun, Earth, and moon at the times of lunar and solar eclipses, as well as new, first-quarter, full, and last-quarter phases of the moon?

Polytene chromosomes form when multiple rounds of replication produce many sister chromatids that remain fused together.

These chromosomal strands are formed after repeated division of the chromosome in the absence of cytoplasmic division. This type of division is called endomitosis.

Specialised cells undergo repeated rounds of DNA replication without cell division, to increase cell volume, forming a giant polytene chromosome. 

Polytene chromosomes have distinct thick and thin banding patterns.

How does polyteny occur?

Mendel's law of independent assortment states that the alleles of two or more different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene.

What is Mendel's law of independent assortment?

A beta particle forms when a neutron changes into a proton and a high-energy electron. 

The proton stays in the nucleus but the electron leaves the atom as a beta particle. 

When a nucleus emits a beta particle, these changes happen:

- the mass number stays the same
- the atomic number increases by 1
- the nuclear charge increases by 1

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