Question – 02
(A) Differentiate between a start and a planet. What is the magnitude of a star, and how the color of stars is correlated with their temperatures?
Answer:
Difference between a star and a planet:
|
Characteristics |
Star |
Planet |
|
Definition |
A
star is a celestial body that possesses light and reflects light on its own.
|
A
planet is a celestial body that does not have an internal source of light.
They receive light from external sources, like sun. |
|
Numbers |
There
are billions and millions of stars present in the Universe. |
Our
solar system that is a part of the known universe has only 8 planets. |
|
Size
and Temperature |
Stars
are huge in size and have high temperature. |
Planets
have relatively small size and low temperatures. |
|
Movement |
Stars
move freely in the universe with a twinkly effect. They do not revolve around
any other star or planet. |
Every
star, like our sun, has planets revolving around it in orbits. |
|
Life
Cycle |
Stars
undergo a life cycle. |
Planets
do not have life cycles. |
|
Examples |
Sun,
Barnard’s star (closest red dwarf star), Sirius star (brightest start in
night sky) |
Mercury,
Earth, Jupiter, Saturn |
The magnitude of a star:
The measure of the brightness of a star is called the magnitude of a star. It is measured with a stellar magnitude scale that ranges from +30 to -30. On this scale, the brightest object has the smallest number, and the faintest object has the largest number. For instance, the star of magnitude -10 is brighter than the start of magnitude +10.
Example: Sirius is the brightest star with a magnitude of -1.46.
Relation between the color and temperature of a star:
The surface temperature of a star determines the color it emits. The color, in turn, depends on wavelength, and wavelength depends on a given magnitude. Thus, According to Plank’s Equation:
Where, E= energy and λ= wavelength of emitted light.
Hence, the blue stars- with a low wavelength- have high energy as well as high temperature, and thus are hot. Whereas the red stars- with a high wavelength- have low energy and low temperature, thus are cold.
For instance, Sirius is a hot star emitting blue light, and Betelgeuse is a cold star that emits red light.
(B) Semiconductors are the Brains of Modern Electronics: Explain in detail what this quotation means.
Answer:
Semiconductors:
Semiconductors are the type of material that has electrical resistance between the resistance of metals (conductors) and the resistance of insulators, as the name indicates “semi-conductor”. It is sometimes referred to as an integrated circuit or microchip made from pure elements like silicon and germanium or compounds like gallium and arsenide.
Semi-conductors in modern electronics:
It is a matter of fact that semiconductors are critical components of millions of electronic devices used in computing, telecommunication, household appliances, banking, security, healthcare, transportation, and manufacturing, etc.
• Computing
Microchips, as used in computers, became the first modern means of computation. Depending on the type of chip, a semiconductor uses binary codes to launch a program or download and save a document.
• Telecommunication
The principle of semiconductors for telecommunication is the same as in computing. A smartphone’s semiconductor chips affect its display, navigation, battery use, 4G reception, and a lot more features. Not just mobile phones, all modern means of communication use semiconductors to function.
• Household appliances
Refrigerators, microwave ovens, washing machines, air conditioners, and other machines around homes and offices operate properly, thanks to semiconductors, in which different chips control temperature, timer, and other automated features.
• Banking
Considering the banking sector, banks are the major investors in microchips as banks deal with digital accounting, cloud platforms, cash withdrawal via ATMs, security cameras, and even automated locking mechanisms.
• Healthcare
Medical professionals, nowadays, make use of advanced technology (semiconductor-based) while carrying out complex surgical procedures, like heart surgeries or organ transplants for accuracy, precision, and safety. Even having discussions with patients, getting their history, and diagnosing them is possible via video conferencing.
In short, semiconductors have, undoubtedly, revolutionized modern electronics and, thus, the way we live.
(C) Briefly describe the most popular and accepted theory about the origin of the Universe
Answer:
There are a number of theories and hypotheses that tried to explain the origin of the universe. However, the most accepted among all is “The Expanding Universe Theory” or “Big Bang Theory” formulated by Georges Lemaitre, a well-known mathematician, and astronomer of his time.
Big Bang Expansion Theory:
According to the Big Bang Theory, the universe is a result of an expansion and is continually expanding.
The theory states the following points:
• Singularity:
Before the creation of anything, there was present a singularity. Singularity means that our Universe was a very dense and hot single point and time and space were zero. Similarly, the matter and energy had same state and temperature was 10 bn. centigrade. Further, gravity was the dominant energy at that time.
• Expansion:
About 13.5 billion years ago, some force suddenly expanded the singularity, resulting in the evolution of time and space. As the space started to expand, the temperature started to cool down gradually as a result of which the energy was converted into the Quarks- the first particle of matter to be formed.
• Formation:
Eventually, the Quarks started making groups and created different sub-atomic particles, which then formed atoms, elements, and molecules in the form of larger chunks. As gravity was present, it converted these irregular chunks into round and elliptical shaped galactic content that, ultimately, lead to the creation of the galaxies, solar systems, planets, etc. This is the universe we see today. The universe is still expanding at an accelerated rate.
Evidence of Big Bang Theory:
Hubble’s Law provides scientific reasoning to the Big Bang Theory and provides the basis for its authenticity. The law explains that the galaxies are continuously expanding without affecting the size of galaxies. Additionally, the presence of cosmic background radiation also supports the theory.
(D) What are the advantages and limitations of renewable energy resources? Briefly explain the prospects of non-conventional energy resources in Pakistan.
Answer:
Renewable Energy Resources:
As the name explains, renewable energy resources are the sources that are continuously replenished. These sources of energy include solar energy, wind energy, geothermal energy, and hydroelectric power. Following are some advantages and limitations of renewable energy resources:
Advantages of Renewable sources of energy:
1. These sources are naturally occurring; therefore, they replenish naturally.
2. They are clean to use as they do not emit carbon and greenhouse gases. Consequently, they minimize global warming and protect our environment.
3. The installation of renewable energy plants creates lot of employment opportunities.
Limitations of Renewable sources of energy:
1. The installation of renewable energy plants is expensive and acquires a lot of resources.
2. The power generation from these sources depends greatly on geographical locations and weather conditions.
3. The storage cost of these energy sources is very high.
Prospects of Non-Conventional Sources in Pakistan:
Pakistan is a country rich in alternative sources of energy and has great potential of non-conventional energy sources. Some of the prospects of non-conventional energy sources are discussed below.
• Wind Energy:
Wind is an abundant resource in Pakistan. Since the country has several well-known wind corridors and an average wind speed of 7.87 m/s in 10 percent of its windiest areas, the country still has a potential installable capacity of around 346,000 MW.
• Solar energy:
Pakistan has tremendous potential to generate solar energy. According to the World Bank, the country can fulfill its current electricity demand by utilizing just 0.071 percent of the country’s area for solar voltaic power generation. Moreover, it can generate more than 2,900 gigawatts of solar power capacity.
• Biomass:
A large amount of solid waste is wasted every year due to improper solid waste management. However, if Pakistan properly manages its solid waste and animal dump, a large amount of biomass can be produced. According to estimation, the potential of biomass energy in Pakistan is 50,000 GW h/year.
Question – 03
(A) Explain with examples the relationship between cells, tissues, and organs.
Answer:
Understanding Cells, Tissues, and Organs and their Relationship
Cells are the simplest units of life that are capable of performing biological functions, and similar types of cells performing a similar function combine to form a tissue. Eventually, the tissues performing similar actions make up an organ.
Examples to Illustrate the Relationship:
1. Muscles:
• Muscle cells, known as muscle fibers, are the basic building block of muscles.
• The two types of muscle cells are skeletal, cardiac, and smooth.
• Different muscle cells combine to form muscle tissues that keep the body upright, move it, and pump the heart.
• Cardiac, skeletal, and smooth muscle tissues form cardiac, skeletal, and smooth muscles (organs) forming the muscular system.
2. Brain and the Spinal Cord:
• Neurons and glia are the basic functional units of the nervous system.
• The neurons and glia combined to form nervous tissues.
• Nervous tissues, muscle tissues, and other tissues to form the Brain and Spinal Cord, which together constitute the nervous system.
3. Heart:
• Cardiac, smooth, endothelial, and connective cells are the basic unit of cardiovascular organs.
• These cells combine to form cardiac tissues, smooth tissues, endothelial, connective tissues.
• Different cardiac, smooth, endothelial, and connective tissues help heart to function properly.
(B) Explain the difference in structure & function between a cell wall and a cell membrane.
Answer:
|
Cell
wall |
Cell
Membrane |
|
Structure
of a cell wall |
Structure
of a cell membrane |
|
The
outermost layer of the plant cell is called the cell wall. |
The
outermost layer of the animal cell is called the cell membrane. |
|
It
is present only in plant cells. |
It
is present in all types of cells. |
|
The
cell wall has a thick and rigid structure with a fixed shape. |
The
cell membrane has a thin and delicate structure with a fixed shape. |
|
Pectin,
cellulose, and hemicellulose from the cell wall. |
It
is made up of 4 types of molecules: proteins, carbohydrates, cholesterol, and
phospholipids. |
|
It
is made up of 35% pectin, 30% cellulose, 30% hemicellulose, and 5%
protein. |
It
is made up of 60-80% protein and 20-40% fat. |
|
The
cell wall is o.1 um thick. |
It
is 7.5- 10 nm thick. |
|
Functions
of a cell wall |
Functions
of a cell membrane |
|
It maintains
the shape of the cell. |
It
maintains the shape of the cell. |
|
The
regulation of the transfer of material into and out of the cell is controlled
by a cell wall. |
It
plays role in the transportation of things into and out of the cell. |
|
It
provides protection to the cell and separates it from its surrounding
environment. |
It
provides internal protection to the cell from the external environment. |
|
It
is fully permeable. |
It
is the porous membrane; however, it is selectively permeable allowing
selective cells to pass into and pass out of the cell. |
(C) What is meant by transpiration? Explain in detail the significance of leaf structure in the process of transpiration.
Answer:
Transpiration:
Transpiration is the biological process by which the excessive water is evaporated from the surface of leaves of plants into the atmosphere in the form of moisture and water vapors.
Role of leaves structure in Transpiration:
Plant leaves have the tiny pores on their epidermal surface that play a significant role in transpiration. These special pores are called stomata. Stomata are microscopic parts consisting of two kidney shaped guard cells. As soon as the water absorbed by the roots reaches the tissues of the leaves through veins, the spongy surface of mesophylls is responsible for taking this water to stomata. Moreover, the 90% of transpiration in plants takes place through stomatal transpiration. In stomatal transpiration, water vapors move through stomata of leaf as the guard cells open and close respectively.
Opening and closing of stomata:
The opening and closing of stomata depend on the turgid or flaccid state of guard cells. In the flaccid state of guard cells, stomata are closed. In turgid state, they are open. Consequently, transpiration occurs when the stomata are open, and it stops when they are closed. Moreover, during daytime, transpiration is more because guard cells are swollen. This swelling caused by the higher concentration of carbohydrates resulting from photosynthesis provides greater area for the release of water. On the other hand, during night time, the guard cells are shrunk providing less area for the release of water.
(D) What is meant by the term double circulation? Briefly describe how the heart is adapted to keep blood flowing in a double circulation.
Answer:
What is double circulation?
The heart has two sides from which the blood flows in and out twice per circuit. This circulation of blood twice per circuit is called double circulation. The right side of the heart pumps the deoxygenated blood from the body into the lungs. On the other hand, the left side of the heart pumps the oxygenated blood from the lungs into the body.
Brief description of the blood flow in heart
As there are two sides in the heart, each side is divided into two atria (upper chambers) and two ventricles (lower chambers).
1. The venae cava, the largest vein in the body, carries deoxygenated blood from the body into the right atrium. From the right atrium, the blood goes into the right ventricle through the tricuspid valve from where it further goes into the lungs.
2. Now, the lungs oxygenate the blood and take it into the left atrium. From the left atrium, oxygenated blood flows into the left ventricle through the bicuspid valve. Afterwards, blood flows from the left ventricle into the body, and aorta, the largest artery of the body, supplies it to the whole body.
Consequently, double circulation in right and left side of the heart takes place simultaneously.
Question – 04
(A) What is the sequence of strata of the atmosphere and on what factors does it depends?
Answers:
What is Atmosphere?
The layers of gases around the earth are called the Atmosphere. In other words, an atmosphere contains the air that we breathe and is a blanket of gases that surrounds Earth. Moreover, it is held near the surface of the planet by Earth’s gravitational attraction.
Strata of Atmosphere:
The atmosphere is comprised of five distinct layers that are determined by the changes in temperature that occurs because of increasing altitude.
• Troposphere: The bottom-most layer of the atmosphere where we live in the troposphere. It extends upward to about 10km above sea level starting from the ground level. It comprises of 75% of all air in the atmosphere; its lowest part is known as the boundary layer while the topmost layer is called the tropopause.
• Stratosphere: Above the troposphere lies the stratosphere. Its distance from the surface of the earth is 12 -50 Km. the ozone layer lies in the stratosphere; the stratosphere is the layer where airplanes fly.
• Mesosphere: The layer of ions is Mesosphere. It extends to a height of about 85km from the ground level.
• Thermosphere: The topmost layer of the strata of the atmosphere is the thermosphere. Its distance from the earth’s surface is 80-320 Km. Satellites orbit Earth within the thermosphere.
• Exosphere: The pseudo or false atmosphere above 500 km is the exosphere. It is the final frontier of the Earth’s gaseous envelope. The exosphere is 10, 000 km from the earth’s surface. However, there’s no clearcut upper boundary where it finally fades away into the space.
Factors affecting the composition of the atmosphere:
The atmosphere is divided into the above layers based on following factors:
1. Temperature and Altitude of the layer
|
Layers |
Temperature
and Altitude |
|
Troposphere |
The
temperature starts dropping as one goes higher in the troposphere. In the
troposphere, temperature drops by 6.5 Celsius degrees per kilometer. |
|
Stratosphere |
Since
the ozone layer comes under the stratosphere, the ozone molecules absorb
ultraviolet (UV) rays from the sun and convert them into heat; consequently,
the temperature of the layer increases. |
|
Mesosphere: |
The
temperature again decreases with increasing height. This is coldest parts of
our atmosphere are located here and can reach around about -90 degrees
Celsius. |
|
Thermosphere |
The
presence of ultraviolet rays and ions (excited atoms) increases the
temperature of the layer. Temperatures in the upper part of the thermosphere
range from 500 degrees Celsius to 2000 degrees Celsius or even higher. |
• Gravity and Pressure in the layer
Another factor that affects the sequence of strata is pressure and gravity. Gravity pulls the molecules in the air towards the earth exerting pressure on molecules. The pressure causes molecules to behave in a specific way. When a parcel of air moves upwards, it expands, and when air expands it gets colder.
• Chemical Composition of the layer
The chemical composition of the layer is also another major factor, which in some ways is affected by the gravity, temperature, and pressure in the respective layers.
(B) Describe the water cycle and briefly explain the major processes involved in the water cycle?
Answer:
What is a water cycle?
The water cycle, also known as the hydrological cycle, describes how the water is exchanged through evaporation from the surface of Earth, rises into the atmosphere, gets colder, and then condenses into raindrops, and, at last, falls back to Earth’s surface as precipitation. It is a continuous cycle that preserves the availability of water on earth. Moreover, this precipitation of water in and out of the atmosphere is a notable aspect of the weather patterns on Earth. Lastly, the water cycle is powered by solar energy and gravity.
Of the many processes involved in the water cycle, the most important ones are Evaporation, evapotranspiration, condensation, precipitation, runoff, and reabsorption.
• Evaporation: Evaporation is one of the major processes in the cycle. Here, the water is converted into gaseous water vapors that occur when the water molecules have attained a sufficient amount of kinetic energy which helps them to eject themselves from the water surface. By evaporation, during the water cycle, all the water from earthly water bodies like seas, oceans, rivers, streams, and lakes in the form of water vapors go into the atmosphere. Factors that are mainly involved in this process are temperature, humidity, wind speed, and solar radiation. Moreover, the statistics show that 90% of water vapors in the atmosphere are formed by evaporation.
• Evapotranspiration: The evaporation of water in the form of water vapors from the bodies of living organisms, like animals and plants, is called evapotranspiration. From plants, water is released through minute pores or stromata present in leaves by a process called transpiration, and from animals, it is released in the process of sweating. The statistics show that 10% of water vapors in the atmosphere are formed by evapotranspiration. Moreover, almost all the water vapors are confined to the troposphere -the bottom-most layer of the atmosphere.
• Condensation: The transition process in which gaseous vapors are converted into liquid or solid is known as condensation. During the water cycle, as water vapors start moving upwards, they start to condense in form of clouds, dew, fog, and frost. They are called the product of condensation. By condensation, water vapors in the atmosphere are released to form precipitates.
• Precipitation: When the product of condensation, such as clouds, falls towards Earth’s surface in large bulk in the form of precipitates, this whole process is called precipitation. It is, then, distributed in four main ways:
• Some of its parts return to the atmosphere by the process of evaporation
• Some may percolate into the soil through the process of infiltration
• Some of its parts may intercept by the process of vegetation which is then evaporated from the leaves’ surface
• Some flow directly as surface runoff into the sea
• Lastly, during the water cycle, since clouds have been formed, they fall to the ground in the form of rain, snow, sleet, and hail.
• Surface Runoff: It is basically the flow of water that occurs on the ground surface when the water from rain, snow, and hail starts moving from greater heights towards the lower areas, and can no longer infiltrate in the soil rapidly. In other words, water that flows from higher to lower levels and finally into oceans instead of getting absorbed into the soil is what we know as surface runoff. For example, rivers, streams, seas, lakes, etc. Moreover, the geomorphological factors involved in this process include the type of soil, area, shape, slope, and network of drainages.
• Infiltration: During surface runoff, some water is infused into subsurface soils, making underground water reservoirs. This process is called infiltration in the water cycle. The result of infiltration is water tables and aquifers. If the aquifers are porous enough that they allow the water to move freely through them, wells can be drilled into the aquifers.
• Re-absorption of water: Plants and animals absorb the underground water that again goes into the atmosphere through evapotranspiration.
(C) What is the difference between asthenosphere and lithosphere? Explain various components of the lithosphere.
Answer:
|
Lithosphere |
Asthenosphere |
|
The
lithosphere consists of the earth’s crust and the uppermost solid layer of the
mantle. |
The
layer of earth where the magma in liquid form is present is called
Aesthonosphere. |
|
The
Continental crust lies above the lithosphere. It overlies the aesthenosphere. |
The
lithosphere lies above the aesthenosphere. |
|
It
has a depth of 100 km with 70 km upper mantle and 30 km crust. |
It
has a depth of 600 km. |
|
As
this layer consists of the tectonic plates, that’s why it is rigid and
brittle in nature. It tends to break and does not flow. |
As
it is a weak and easily deformed layer, this layer, therefore, acts as a
lubricant for the plate tectonics to slide over. It tends to flow like
toothpaste. |
|
It
consists of different elements and minerals. |
Since
it is molten lava and magma, it contains only iron-magnesium silicate. |
Components of the lithosphere:
The lithosphere, the rigid and outermost shell of the earth, is essentially comprised of two main elements:
1. Crust:
• The lithosphere contains crust which is its lightest, most buoyant layer. It further comprises of continental and oceanic crust.
• The Continental crust is significantly thicker (20 to 80 km) than the oceanic one (5 to 10km) and its upper part is more exposed as compared to its lower part. It is comprised of granite rock that is lighter in color. It mainly constitutes silicon, aluminum, and oxygen.
• Oceanic crust is that part of the Earth’s crust that comprises dark-colored rocks which are made up of silicon, oxygen, and magnesium. Moreover, it scarcely floats on the mantle.
2. The upper and lower mantle
• The upper mantle is located beneath the crust of the Earth and ends at the lower mantle. It is responsible for the movement of tectonic plates, earthquakes, and volcanoes. Its thickness is round about 200 to 250 miles. Here, the temperature ranges from 900 to 1600 degrees Fahrenheit. The upper mantle is not homogenous throughout. Its lowest layer of the upper mantle is known as the aesthenosphere which comprises of fluid and is able to move. This fluidity causes the tectonic plates to move.
• The lower mantle is located approximately 400 to 1800 miles below the earth’s surface. It makes up the most bulk of the entire mantle. It contains solid rock and minerals. It is located above the outer core. Additionally, the lower mantle is extremely hot around about 7000 degrees Farenheit because it helps in transferring heat from the core to the upper mantle.
This part of lithosphere, as a whole, is about 1800 miles thick. The magma in its solidified form is present in Lithosphere. Moreover, to scientists, the mantle is a crucial part of the interior of earth.
(D) Differentiate between food contaminants and food adulterants.
Answers:
|
Food
contaminants |
Food adulterants |
|
Definition:
Food contaminants are unwanted and impure elements in food, mainly introduced
by the environment through humidity, heat, water contents, or soil etc.
Moreover, they also include any harmful substances that are unintentionally
added to food, which maybe chemicals from natural resources or formed during
food processing. |
Definition: Food adulterants are inferior, substandard, or unnecessary
substances deliberately added to food to improve its appearance and to gain
greater profit. |
|
Examples:
Heavy metals in soil, which plants take up, are present in vegetables and
fruits as food contaminants. Similarly, exposing food to high
temperature provides a favorable environment for pathogens and bacteria to
grow, ultimately contaminating the food. If the fields are sprayed with
contaminated water for irrigation, fruits and vegetables can be contaminated
before harvesting. |
Examples:
A chemical named melamine is commercially added to milk to increase its
protein level. Tea leaves are usually adulterated with used tea leaves
that are processed and colored. To enhance the flavor and color of
honey, companies mix molasses sugar with it. Injecting water or brine into
meat to increase its weight is also an example of food adulteration. |
|
In
most of the cases, containment of food happens naturally. |
Adulteration
of food is completely a man-made process. |
|
Food
containment is an unintentional process. |
Food
adulteration is done intentionally. |
|
It
does not have any economic gains. |
It
is motivated by economic gains. |
Question – 05
(A) Define the term “malnutrition: Elaborate its major causes and consequences.
Answers:
Definition of Malnutrition
Malnutrition, in all its forms, refers to the deficiency, excess, or imbalance of the nutrients in a person’s diet. The term is used to refer poor nutrition and overnutrition. However, it commonly refers to undernutrition, a condition when a person does not intake right number of dietary intakes -a condition when the body is deprived of vitamins, minerals, and other nutrients that are significant to maintain the tissues, cells, and bones healthy.
Major causes of Malnutrition
There are various factors that can lead to malnutrition:
1. Acquired Causes: In this case, a quantitatively inadequate diet, mainly in calories or protein, is the main factor behind malnutrition. I.e.,
• Unavailability of sufficient food
• Inadequate agricultural processes
• Imperfect distribution of food
• Malabsorption of vitamins, such as A, K, and D, minerals, and nutrients
• Poor eating habits and food preferences
2. Role of metabolic defects:
Malnutrition can also arise from acquired or inherited metabolic defects, notably those involving the digestive tract, liver, kidney, and red blood cells, etc.
Consequences of malnutrition
3. Social consequences
• Child malnutrition: Undernourished children have weak immune systems; therefore, they are prone to many diseases, like diarrhea, anemia, stunting, rickets, etc.
• Adult malnutrition: Improper intake of nutrients badly affects an adult’s weight, height, eyesight, health, and other mental capabilities.
4. Economic consequences
• Malnutrition slows economic growth and perpetuates poverty.
• Morbidity and mortality due to malnutrition cause loss in human capital and productivity.
(B) Explain how a slice of bread after few days decomposes due to the growth of fungi.
Answers:
A fungus called bread mold is responsible for the bread decomposition. When bread is kept in warm temperature for a few days, mold grows on bread.
How does mold decompose the bread?
Since there are tiny spores present in the air, they fall on the slice of bread and the mold starts to grow. These spores germinate to form hyphae that release secretive enzymes on the particles of bread and break them down into smaller pieces. Afterward, mold absorbs the moisture and nutrients from the bread and starts to spread throughout the bread decomposing the bread.
Factors accelerating the growth of mold
1. Temperature:
Temperature is the most important factor determining the growth of mold. It grows faster in warm temperatures; therefore, it can be prevented by keeping the bread in the refrigerator.
2. Moisture:
Moist bread is likely to decompose faster.
3. Acidity:
Mold grows more in acidic foods. Bread with a higher ph value is less likely to decompose. If the pH value is less than 7, mold grows faster.
(C) What is computer memory? Describe its units and discuss various types of memories.
Answers:
What is computer memory?
Computer memory is the storage space where the computer stores data, instructions, and programs. These memory spaces keep the data that is to be processed and the instructions required for processing. Moreover, a computer stores the data in specific locations with unique memory addresses.
Computer Memory Units
The units that represent how much data can be stored in a computer are called memory units. Following are some of the memory units:
• Bit: it is the smallest memory unit that stores two digits 0 and 1.
• Byte: 8 bits make one byte. However, a byte can store multiple characters, alphabets, digits, etc. it is also a pattern that stores data in numbers between 0 and 255.
• Kilobyte: 1024 bytes makes 1 kilobyte. It stores up to 1000 characters.
• Megabyte: 1024 kilobytes make 1 megabyte. It stores 1 million characters.
• Gigabyte: 1024 megabytes make 1 gigabyte. It stores 1 billion characters.
• Terabyte: 1024 gigabytes make 1 terabyte. It stores 1 trillion characters.
Types of computer memory:
There are various types of computer memory: Cache Memory, Primary Memory, and Secondary Memory.
• Cache Memory
The memory that acts as a buffer between CPU and main memory is called cache memory. The programs that are most frequently used by CPU are kept in this memory. Therefore, it increases the speed of the CPU.
• Primary Memory (Main Memory)
Primary memory holds the data and instructions on which a computer is currently working. They are volatile memories since data is lost when the computer is switched off. RAM and ROM are examples of main memory.
• Secondary memory
The external or non-volatile memory of a computer is called secondary memory. The data and instructions are permanently stored in them. Also, CPU does not directly access them; instead, they are accessed through input-output devices. DVD, CD-ROOM, USB, is some examples of secondary memory.
(D) Differentiate between natural and artificial satellites. Briefly describe the working of communication satellites with some applications.
Answer:
|
Natural
Satellites |
Artificial
Satellites |
|
The
satellites that exist naturally in the space are called natural satellites. |
The
man-made satellites serving human for various tasks are called artificial
satellites. |
|
Earth’s
moon is an example of natural satellites. |
The
communications satellites created by humans for communication are examples of
artificial satellites. |
The working of a communication satellite with examples:
Communication satellites use high-frequency and high-wavelength waves called radio waves to send and receive signals.
Communication satellites have two transmission systems to communicate with earth:
1. Uplink: The transmission of signals from earth to the satellite is called uplink
2. Downlink: whereas the transmission signals from the satellite to the earth are called downlink.
Moreover, the communication to and from the satellite is done in three steps:
1. Sending signals from earth station
2. Retransmitting signals from satellites
3. Receiving signals on satellite footprint.
Applications of communication satellite
1. Television satellite:
To watch a cricket match, live from England in Pakistan, the signals from the earth station, and the stadium, are sent to the television satellite. The satellites receive, interpret, and retransmit the signals to the earth station in the coverage area of Pakistan. The coverage area, known as satellites footprint, includes various television stations in Pakistan that receive signals through antennas and send to television sets in houses.
2. Radio satellite
Similarly, to listen to a podcast on radio, the signals from radio station are sent to the satellites. Radio satellites receive, interpret, and retransmit the signals to the satellite footprint of the area where the podcast is being heard. Moreover, the frequency of the radio set catches the frequency of radio station through antennas to play the podcast.
3. Mobile phone satellites.
These satellites work on the same principle of communication satellites. The voice from one mobile tower is sent to the mobile satellite which retransmits the signal to the other mobile tower through antennas.
