Why are the leaves green in colour?

The young leaves are light red in colour and they change into green colour after few days. Why? When anything absorbs or reflects the colours of the sunlight, it gets its colour.

Chlorophyll and carotene are the two pigments present in leaves. The leaves look green due to chlorophyll and yellow due to carotene. The colour of the leaf changes according to the ratio of these two substances (pigments). Very young leaves have red colored pigment called anthocinin, thus, they look red. In due time, chlorophyll and carotene are produced and then the colour of the leaf is changed. When sunlight falls on the leaves, except green colour (from 7 VIBGYOR colours) all the other six colours are absorbed and green is reflected. Thus, we can see leaves in green colour. Leaves without chlorophyll cannot prepare food on their own.

Equation of Photosynthesis

Here, utilizing the light energy, simple compounds are transformed to new compound. Let’s see:

Photosynthesis as a Process

We can't see anything without light. It is a form of energy. Plants use this energy to prepare food by utilizing other factors necessary.

We often feel that the water we pour to the plants is the source of food for them. But water is one of the factors of photosynthesis.

The nutrient chemicals in the water are transformed to carbohydrates with the help of chlorophyll in the leaves. The water from the land is sucked (absorbed) and transported to all parts of the plant through the stem, by the roots.

Leaves absorb CO2 from the environment, with the help of sunlight; they split CO2 to carbon and oxygen. They combine nutrients with carbon to prepare carbohydrates.
Even though a plant has green leaves, nutrients, CO2 it can't prepare food in the absence of any other factor also (like CO2, chlorophyll, water).

It is estimated that approximately 150-200 tons of carbon element is used by the leaves every year during photosynthesis.

Whatever may be the food item (rice, pulses, vegetables, fruits, nuts etc.,) we use in food (which come from plants) is prepared by photosynthesis.

Thus leaves are considered as food factories of the plant.

Photochemical Reaction

Living forms have some basic processes which help in the survival and perpetuation of race called life processes. Photosynthesis one of it where green plants synthesis carbohydrates utilizing external factors like sunlight and CO2 and internal factors like water and chloroplasts, in leaves which are the main sites of photosynthesis. Oxygen is liberated in this process, which makes our living possible.

Roger Bacon, known as the founder of experimental science said "Doing experiments for your self is the way to learn about nature". Trying to experiment whenever, you can, helps a lot in enhancing your scientific attitude.

Set your mind and let yourself enter into the world of Biology to learn more, to attain long term retention so that you can gain success.
Photosynthesis is a photo-chemical reaction where plants utilize Sunlight, CO2, Chloroplasts, Water, Enzymes, Mineral and Salts etc., to prepare their own food (Carbohydrates).

The different types of Fractures seen in the Limbs of a Person

The term fracture is used to indicate that the bone is broken due to an accident. Fractures can occur in any part of the body, but usually they occur in the limbs. The following are the different types of fractures.

1. Simple fracture: This is also called closed fracture. Only the bone is broken and there will not be wounds at the site of fracture. The bone may be broken completely or partially.

2. Compound fracture: This is called open fracture. Along with the fracture of the bone, wound is also seen at the site of the fracture. One or both the broken ends of the bone pierce through the skin and protrude out. This may damage the surface tissue and cause bleeding.

3. Complicated fracture: This type of fracture is associated with damages to important internal organs such as liver, brain, intestines, spleen and major blood vessels.

4. Communicated fracture: In this type, bone is broken at several places.

5. Impact fracture: The broken ends of fractured bone driven into another.

6. Green stick fracture: The bone bends but does not break. This is usually seen in children.

The rules to be followed while giving FIRST AID

The following rules and principles are necessary for success in first aid and to save the victim from danger.
1. Organize the activities in orderly fashion without panic and confusion.
2. Firstly, treat for breathing. Every second is important for the survival of the victim.
3. If the victim is bleeding, immediately make efforts to stop it.
4. Treat for the shock by moving the victim as little as possible and handling gently.
5. Do first aid as much as required to prevent the deterioration of the condition.
6. Do not allow people to crowd around the victim. Allow fresh air to the victim.
7. Do not create fear in the victim or people around him. Assure him that he is in safe hands and medical help will be coming soon.
8. Do not move or remove clothes from the victim unnecessarily.
9. See that proper medical help is available to the victim at the earliest by sending message to a doctor or to an ambulance.

Plant Ecology

Ecology is the branch of biology which deals with the study of distribution, structure and interaction of organisms with their environment. The term ‘ecology’ was coined by Reiter. Ecology is derived from two Greek words ‘olikos’ meaning house and ‘logos meaning study. According to warming ‘ecology is the study of organisms in relation to their environment’.

According to odum ‘ecology is the study of organisms I relation to their environment’.

Different levels of organization in ecology are:
Cells- tissues- organs – organ systems - organism - population – community - ecosystem - biosphere.

Population: it sis a group of similar individuals belonging to the same species found in an area.

Ecosystem: it is the structural and functional unit of nature. The interaction between the biotic and abiotic components is called an “ecosystem”.

Community: A community is an assemblage of all the populations belonging to different species occurring in an area.

Warming classified plant communities on the basis of water relations into three categories:
Hydrophytes, Mesophytes and Xerophytes

Hydrophytes: The plants which grow in water or very wet places are called hydrophytes. They may be further classified into
1. Free floating (Pistia)
2. Rooted hydrophytes with floating leaves (Nelumbo)
3. Submerged suspended (Hydrilla)
4. submerged rooted (Vallisnaria)
5. Amphibious plants (Sagittaria)

Hydrophytes show certain morphological and anatomical adaptations to survive in water. Generally the hydrophytes have poorly developed roots, slender stems, dissected or floating leaves and some of them show hererophylly. Internally the hydrophytes lack cuticle and stomata, the mechanical tissues like collenchyma and sclerenchyma are less developed, poorly developed vascular tissues and aerenchyma is well developed.

Xerophytes: the plants which grow in habitats where water supply is deficient or soil is physiologically dry are called “Xerophytes”. They are classified into:
1. Ephemerals (Tribulus)
2. Succulents (Opuntia)
3. Non-succulents (Calotropis)

Xerophytes also show certain morphological and anatomical adaptations to over come water deficit. Generally they have well developed root system, short and stunted stems and reduced leaves (spines or scales). Internally they possess thick cuticle, multilayered epidermis, waxy coating on the epidermis, hypo stomatal condition, and we developed mechanical tissues and vascular tissues.

Types of Forces

Push or Pull is called a force
              A force is a push or a pull which can affect the motion of an object by changing its speed or direction. If two equal and opposite forces act on an object it may be squashed or stretched. Both the magnitude and direction of force acting on an object must be stated, because both affect the way in which the object moves. If the direction in which a force is acting is known, it is possible to predict the way the object it affects may move. Forces are represented by arrowed lines whose length corresponds to the magnitude of the force. The arrow indicates the direction in which it is acting. Force is measured in Newtons (N).

Magnetic and Electrical Forces:

Magnets can exert a force of attraction and repulsion

There are two types of forces which act at a distance: magnetic and electrical forces. Objects which extra a magnetic or an electrical force can attract or repel objects which are brought near them. The region in which the forces act is called a field. The magnitude of the forces depends on the distance between the objects. The closer they are together, the stronger the forces they exist. 
Frictional Forces:

 Friction between the tyres and the road
                 Friction is the force which resists the motion of two materials rubbing together. Sometimes it is useful force – for example, it enables us to grip the ground as we walk. A vehicle is able to grip the road due to the friction between its tyres and the road surface. But friction also has unwanted effects. The friction between the moving parts of a machine produces heat which wastes energy. The friction between a cyclist and the air resist his or her forward movement.
Gravitation and Weight:

                 Gravitation is another force which acts at a distance. It is the force which exists between any two masses, attracting them towards each other. Usually it is a weak force, but if one object is massive, such as a planet, the force becomes noticeable. Gravitational force depends on the distance between objects. The closer the objects are together, the stronger the force they exert on each other.
             Weight is a measure of a planet’s gravitational pull on an object. Like all forces, it is measured in Newton’s (N). The weight of an object depends on its distance from a planet and the planet’s mass. On the Earth’s surface, the force of gravity acting on a mass of 1 Kg is approximately 9.8 N. The magnitude of the force diminishes as the mass moves further away from the Earth’s surface. An object’s mass, however, remains the same wherever it.
Force is Proportional to Elastic
Graph between Force and Extension
When a force is applied to an object which cannot move, the object stretches. Its molecules are pulled slightly apart and it becomes distorted. If the object remains distorted when the force is removed, its distortion is called plastic. If its molecules return to their original position, the distortion is called elastic. Elasticity is, therefore, a material’s ability to return to its original shape. To study the elasticity of a material, such as a strip of copper, rubber or nylon, weights of increasing size are suspended from the material. The amount by which the material is stretched is found by subtracting its original length from its extended length. The size of the force is then increased and the results are used to make a graph.

Hooke’s Law:

               Hooke’s law states that the extension of a material is proportional to the force which is stretching it.
              There is a point, however, beyond which Hooke’s law is no longer obeyed. This is called the limit of proportionality. If the substance is stretched further than this point, it reaches its elastic limit. The substance stops being elastic and remains distorted even when the stretching force is removed.
             Provided a material’s elastic limit is not exceeded, the principle of Hooke’s law can be used in calculations to determine an unknown force or extension.
              For example, if a force of 10N stretches a spring by 60mm, the force which would produce an extension of 42mm is calculated as follows:
60mm extension produced by 10N
1mm extension is produced by 10/60

            Therefore, the force which would produce a 42mm extension is calculated as follows: 10X42/60 = 7N

A Spring Balance:

The easiest way of measuring forces is to use a spring balance, after called a Newton Balance. This is a device containing a spring. The spring obeys Hooke’s Law. This means that it stretches in direct proportion to the force applied to it. For example, if the forces applied to the spring are doubled, its extension doubles. The spring balance will measure forces accurately until it is stretched beyond its elasticity limit and it becomes permanently distorted.
Scalar and Vector Quantities:

               Quantities in physics are described as either scalar or vector quantities.
               A scalar quantity is one which has magnitude only. For example, Mass and Temperature are scalar quantities.
              A vector quantity is one which has both direction and magnitude. Force is a vector quantity. The magnitude and direction of a vector must always be stated. Vectors can be represented with arrowed lines.


Q: What is an earthquake and what causes them to happen?

Ans: An earthquake is caused by a sudden slip on a geological fault line. The tectonic plates are always slowly moving, but they get stuck at their edges du to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the Earth’s crust and cause the shaking that we feel.

Q: What’s the difference between foreshocks and aftershocks?

Ans: “Foreshock” and “aftershock” are relative terms. Foreshocks are earthquakes that precede larger earthquakes in the same location. Aftershocks are smaller earthquakes that occur in the same general area following a larger event or “main shock”.

As a general rule, aftershocks represent minor readjustments along the portion of a fault that slipped at the time of the main shock. The frequency of these aftershocks decreases with time, but they can go for weeks or some times months.

Q: Can the position of the Moon or the Planets affect seismicity?

Ans: The Moon, Sun and other planets have an influence on the Earth in the form of perturbation (small changes) to the gravitational field. Many studies in the past have shown no significant correlations between the rates of earthquakes occurrence and the seme-di-urnal tides when using large earthquake catalogues.

Dos and Don’ts:

1. If indoors, drop to the ground. Take cover by getting under a sturdy table or other piece of furniture. If there is no desk or table, cover the face and head with arms and crouch in an inside corner of the building.

2. If outdoors, move away from buildings, trees, street lights and utility wires.

3. If in a moving vehicles, stop as quickly and stay in the vehicle.

4. If trapped under debris, do not light a match; do not move about or kick up dust; tap on a pipe or wall so rescuers can locate you.

5. Use a whistle if one is available. Shout only as a last resort. Shouting can cause you to inhale dangerous amounts of dusts.

Nepal Earthquake Images

Genetically Modified Organisms

What are GM foods?

Genetically modified organisms (GOMs) can be defined as organisms (i.e. plants, animals, or microorganisms) in which the genetic material (DNA) has been altered in way that does not occur naturally by mating and/or natural recombination.

One of the objectives for developing plants based on GM organisms is to improve crop protection. The GM crops currently on the market are mainly aimed at an increased level of crop protection through the introduction of resistance against plant disease caused by insect or viruses or through increased tolerance towards herbicides. Resistance against insects is achieved by incorporating into the food plant the gene for toxin production from the bacterium bacillus thuringinensis (Bt). This toxin is currently used as a conventional insecticide in agriculture and is safe for human consumption.

Commercial sale of genetically modified foods began in 1994, when Calgene first marketed its Flavr Savr delayed – ripening tomato. Most food modification have primarily focused on cash crops in high demand by farmers such as soyabean, corn, canola and cottonseed oil.

The safety of such products is not verified yet, in fact, we are the lab rats to test the safety of such technology. It is feared food and water contaminated with genetically engineered material could increase the growth of malignant tumors upon contact with humans. Genetic engineering allows introducing animal products in plants which could raise issues for those with dietary restrictions, like vegetarian or vegans. Pesticide resistant food can create super- creature! It’s not a joke, modified genes in engineered crops that resist pesticides can transfer to insects and pest; making them pesticide resistant. These super-organisms cannot be controlled easily. India placed a moratorium on GM aborigine in 2010. Fearing the effect on food safety and biodiversity. Field trials of other GM crops were nat formally halted, however. The GM mustard planted in the half-acre field in the grounds of the Indian Agricultural Research Institute in New Delhi is in the final stage of trials Launched in 2002, Bt cotton, which produces its own pesticide, is the country’s only GM crop and covers 95 percent of India’s cotton cultivation of 11.6 million hectares (28.7 million acres).

Quiz on Dynamics

Test Your Knowledge
This is a test of your knowledge. You’ll find the answers at the end of the quiz.
Fill in the blanks.
1. Newton's laws are valid in --- frame of reference.
2. --- force is a pull on the body towards the centre of the circle.
3. Circular motion is a special case of ---- motion.
4. In a uniform circular motion --- is constant.
5. Centrifugal force means ---- force
6. Centre seeking force is called ---
7. If the string of Whirling stone is cut, the stone moves in ---- direction.
8. Satellite communications use --- waves
9. Centripetal acceleration, a = ----
10. The angle subtended by an arc of unit length on a circle of unit radius is called ---
11. In SHM, the acceleration of the particle is directly proportional to ---
12. A body executing oscillatory motion comes to rest at ----
13. Periodic motion is also called as ---
14. If a particle in periodic motion moves back and forth over the same path, its motion is called ----.

1) inertial         
2) Centripetal           
3) Rotatory         
4) Angular Velocity        
5) Fictitious
6) Centripetal force    
7) Straight line or tangential to the circle     
8) Microwaves  
9) a =  v2/r
10)  a radian            
11)  Its displacement                
12) The equilibrium position
13) Harmonic motion                       
14)  Oscillatory or Vibratory motion.

Simple Harmonic Motion and its Characteristics

Simple Harmonic Motion: 
The to and fro motion of a particle about a mean position on a fixed path such that the acceleration of the particle is always directed to the mean position and is directly proportional to the displacement of the particle from its mean position is called Simple harmonic motion.

Characteristics of SHM:
1. A constant time period (T) (or) a constant frequency υ = 1/T
2. An amplitude (A)
3. A constant mechanical energy which is the sum of potential energy and Kinetic energy at every point in the path of oscillation.

Centrifugal Force

Centrifugal Force:
1. It acts normally on the same particle executing uniform circular motion.
2. It is directed radially away from the centre of the circle.
3. It cannot be associated with any agent.
4. It is a fictitious force in an inertial frame of reference.
5. It is the tendency of the body to fly away from the centre of the circle.
6. It comes in to play in a rotating frame of reference.
7. In a uniform circular motion, its magnitude is constant and equal to that of the centripetal force.
8. Centrifugal force depends on mass 'm'. Hence bodies of higher mass rotate on a circle of higher radius (principle of centrifuge).

Centripetal Force

Centripetal Force:
1. It acts normally on a particle executing a uniform circular motion.
2. It is always directed radically towards the centre of the circle.
3. It is associated with an external agent.
4. It is a real force in an inertial frame of reference.
5. It is a pull on the body towards the centre on a curved path.
6. It is necessary to make a body to travel on a curved path.
7. In a uniform circular motion, its magnitude is constant.
8. Centripetal force depends on mass of a body in a circular motion with speed V.

Centrifuge and Laundry Drier

1. A centrifuge is a machine used to separate particles of higher mass from those of lower mass in a given mixture.
2. A centrifuge consists of a cylindrical vessel rotated about its own axis at high speed with the help of an electric motor.
3. When milk is poured into the cylindrical vessel of the centrifuge and rotated with high speed, the particles of higher mass (skimmed milk) are thrown away from the centre due to greater centrifugal force and lower-mass cream particles collect at the centre, that is, near the axle.

Laundry Drier:
1. The wet clothes are dropped into a cylindrical vessel containing holes.
2. When the vessel is rotated, the wet clothes get struck to the walls of the vessel.
3. The centrifugal force pushes the water molecules out from the clothes through the holes.
4. In this way the clothes are dried.

Principal of Artificial Satellites and their Uses

Principle of Orbiting Satellite:
1. A satellite is a natural or artificial body orbiting around another body of larger mass and larger radius.
2. Moon is a natural satellite of earth.
3. When a sufficient horizontal speed is imparted to a body it revolves round the earth. This is the principle of launching an artificial satellite.

Uses of Artificial Satellites:
1. Artificial satellites help to develop reliable communication links over the entire globe.
2. They are used to the 'Weather Prediction'.
3. Satellites and space stations are used for the study of astronomy.
4. The artificial satellites are used for remote sensing.
5. Telephones, Fax, Internet are some examples for global communications.
6. Artificial satellites are also used for spying in the defense service.

Quiz on Screw Gauge

Test Your Knowledge
This is a test of your knowledge. You’ll find the answers at the end of the quiz.
Fill in the blanks.
1. Least count of an ordinary scale is .......
2. Screw gauge works on the principle of a ............
3. The scale marked on the index of a screw gauge is called ...............
4. Screw gauge consist of ...........and........
5. The distance traveled by the tip of a screw for one complete rotation of its head is called......
6. If the zeroth division of the head scale is below the index line of the pitch scale, the error is said to be ............ and the correction is ................
7. If the zeroth division of the head scale is........ , the index line of the pitch scale, the error is said to be negative and the correction has to be........
8. In the screw gauge the other end of the barrel is tapered and has 100 (or) 50 equal divisions on it, is called the ...........

1. 1 mm       
2. Screw in a net        
3. Pitch scale
4. Head scale , Pitch scale         
5. The pitch of the screw             
6. Positive, negative    
7. Above, positive       
8. Head scale

Uses of a Screw Gauge

Uses of a screw gauge:
  • The thickness of a metal sheet is expressed in gauge number. By finding the thickness of a metal sheet in m.m. by using a screw gauge, we can know its gauge number. For example, if the thickness of a sheet is 5.16 m.m., then the gauge number will be 6. If the thickness of a sheet is 0.953 mm, then the gauge number will be 10. To know gauge number for various thickness use a conversion table.

  • The diameter of a wire is expressed in American wire gauge size. By finding the diameter of a wire after removing the insulation of the wire in mm by using a screw gauge, the gauge size can be obtained. For example, if the metric size of a wire is 52 mm, then A.W.G. size will be '0'. If the metric size of a wire is 5 mm, then A.W.G., size will be 10. To know A.W.G. size for various metric sizes of a wire use a conversion table.
  • Screw gauge is used to find the diameter of a steel rod that is used in the construction of a building.
  • It is used in the industry to manufacture components of a machine with required measurements.
  • As this instrument is used to measure the gauge of a metal sheet or a wire, it is named as screw gauge.