TOTAL INTERNAL REFLECTION

Total internal reflection can occur when light travels between two media from the medium with the higher refractive index into the medium with the lower index of refraction. There is a critical incident angle at which Snell's law predicts the refracted angle will be 90 degrees. At incident angles greater than this critical angle, light can not be refracted into the medium with the lower refractive index. Hence all the light striking the surface must be reflected. We have total internal reflection. The critical angle is given by the formula: sin(theta critical)=(n2/n1), where n1 is the larger refractive index and n2 is the smaller.

Total internal reflection can only occur when light is trying to travel from a material with a high refractive index into one with a lower refractive index. It will not occur when traveling from a low refractive index to a higher refractive index. For example, light traveling from glass to air might experience total internal reflection, but light traveling from air to glass never will. The greater the difference in refractive index between the two materials, the more likely there will be total internal reflection.

Fiber optic cables use total internal reflection inside the optical fiber. The light enters the optical fiber, and every time it strikes the edge of the fiber it experiences total internal reflection. This way the light travels down the length of the optical fiber.

Binoculars and other optical instruments often use prisms to reflect light. The light enters the prism in such a way that it will strike the other side of the prism and be totally internally reflected. The prism can in this way act as a mirror.

Rainbows form when light enters raindrops. The light is totally internally reflected inside the raindrop before leaving. In addition the light of different colors is refracted at different angles to separate the colors in an effect called dispersion.

The brilliance of diamonds results from light entering the diamond and being totally internally reflected from the opposite side before exiting in approximately the original direction.




source
http://atomic-molecular-optical-physics.suite101.com/article.cfm/optics_total_internal_reflection

Effect of space on Human body

1) Effect on cardiovascular system  

Human beings living on Earth are affected by gravity because about two-thirds of our daily activities are standing or sitting. Because of this great amounts of body fluids such as blood pool in the lower part of the body. The human body is equipped with various mechanisms to oppose gravity to maintain sufficient blood flow to the brain.
In micro gravity environment, the quantity and the distribution of body fluid alters since it is free of the gravitational effect. This is the known as "fluid shift." Symptoms caused by fluid shift are stuffy nose, headache, and puffy face.  

2) Effects on bone  

Bones are systems involved in maintaining posture. The adult human body has 1,000 to 1,200 grams of calcium and 400 to 500 grams of phosphorus. However, once gravitational stress is removed, bone calcium and phosphorus are excessively excreted in urine and faeces. It is seen that 3.2% of average bone loss occurred after nearly 10 days of weightlessness. The loss of calcium in urine may produce urinary stone, which might cause severe pain, the decrease of bone density will lead to bone fracture. Therefore, countermeasures are necessary.
One countermeasure proposed to prevent bone loss is onboard exercise mainly with thetreadmill and ergo meter.  

3) Effects on muscle  

The human body floats within the orbiting spacecraft. Therefore, astronauts can move around in spacecraft just by softly pushing against its wall. In a micro gravity environment, muscles rapidly weaken due to the lack of use.  

4) Space motion sickness  

A few minutes or a few hours after entering weightlessness, astronauts experience space motion sickness, which is characterized by headaches, malaise, nausea and vomiting. Sixty to seventy percent of the astronauts experience these symptoms.  

5) Effect on hematologic and immunologic system  

One significant alteration in the hematologic and immunologic system in micro gravity is the transformation of red blood cells, the main component of blood. Ninety percent of our normal red blood cells have a biconcave discoid shape (i.e.) a doughnut without a hole. In weightlessness, some red blood cells transform into "mulberry" or spherical shape. However, they are readily reversed even after long-term space mission.  

6) Effects of space radiation  

Space radiation exists in the space environment. On the Earth, the atmosphere and magnetic field provide a shield for humans, and prevent space radiation from penetrating to the Earth's surface. Due to the absence of such shielding in the space environment, astronauts are subjected to greater amounts of space radiation than they would receive on the Earth. Therefore, the space radiation may seriously affect the astronauts.

source

http://library.thinkquest.org/03oct/02144/propulsion/principle.htm

summary of the lectures on 26th

FOR IGCSE

8th -  Problem solving on graphical method of representing motion.
key points - area under the curve of Speed time graph gives you distance.
for finding the gradient of speed time graph should have a big triangle on the curve to find the acceleration from the graph.

9th - Dispersion from the prism
White light enters in the prism and split into 7 colors
where RED deviate least and the VIOLET deviate most
Thats why the red light is used to represent the danger sign.

.....................................................................................................................................................................
IB

The elastic collision
An elastic collision is an encounter between two bodies in which the total kinetic energy of the two bodies after the encounter is equal to their total kinetic energy before the encounter. Elastic collisions occur only if there is no net conversion of kinetic energy into other forms.

An inelastic collision is a collision in which kinetic energy is not conserved (see elastic collision).

In collisions of macroscopic bodies, some kinetic energy is turned into vibrational energy of the atoms, causing a heating effect, and the bodies are deformed.

The molecules of a gas or liquid rarely experience perfectly elastic collisionsbecause kinetic energy is exchanged between the molecules' translational motion and their internal degrees of freedom with each collision. At any one instant, half the collisions are – to a varying extent – inelastic (the pair possesses less kinetic energy after the collision than before), and half could be described as “super-elastic” (possessing more kinetic energy after the collision than before). Averaged across an entire sample, molecular collisions are elastic.

Today's 23rd July class for 9th IG/8th IG

Dispersion phenomenon

The amount of refraction of light at a boundary between two media depends on three things:

1. The nature of the media (embodied in a characteristic quantity called the index of refraction for a medium).
2. The angle of indidence for the light ray on the boundary.
3. The wavelength of light.

The dependence of refraction on the wavelength of light is called dispersion. This dependence has both positive and negative implications for astronomy. On the positive side, it is the basis for the prism and its ability to separate light according to wavelength; on the negative side, it is the source of chromatic aberration in optical devices (the failure of different wavelengths to focus at the same point).


FOR 8TH IGCSE


The shapes of the velocity vs. time graphs for these two basic types of motion - constant velocity motion and accelerated motion (i.e., changing velocity) - reveal an important principle. The principle is that the slope of the line on a velocity-time graph reveals useful information about the acceleration of the object. If the acceleration is zero, then the slope is zero (i.e., a horizontal line). If the acceleration is positive, then the slope is positive (i.e., an upward sloping line). If the acceleration is negative, then the slope is negative (i.e., a downward sloping line). This very principle can be extended to any conceivable motion.
The slope of a velocity-time graph reveals information about an object's acceleration. But how can one tell whether the object is moving in the positive direction (i.e., positive velocity) or in the negative direction (i.e., negative velocity)? And how can one tell if the object is speeding up or slowing down?

DISCUSSION with PRASANTH (IBDP physics student)

PRASHANTH

sir,

the concept of time travel is some what like this:

if the whole universe is rotating...and light reflected from u is travelling in all directions...then at some point of time when u reach the other side of the universe u will be able to see urself..or rather the past..but this is almost impossible

neways time travel has lost momentum..

now its time for quantum computing...

its abt arranging atoms and bombarding them with photons to perform complex calculations..

but the basic requirement for a quantum computer is to calculate 5x3=15

Deepak sir

I agree but its a weak theory ...

The quantum theory suggestion is there is a parallel universe exist with ours ... and probably we are in the parallel universe probably advanced or not so advanced .

now the question is how many parallel universe 

is it infinity 

so thinking on parallel universe we need to travel faster than time and reach in any parallel universe either past or future 

thats why i gave a simple example where it can make a i dea of time machine to be logical

we still don know how and where ....

but thats how the research begin

PRASHANTH

sir,

the idea of travelling faster than time seems impossible as we cannot travel faster than the speed of light..

there are some physical limits which can never be achieved like -276k or faster than the speed of light or finding out the exact location of any particle at a given time. 

on the other hand a single unified theory that relates all other theories is being worked on.

this is the string theory..which suggest that every particle is made up of strings and the direction or type of vibration causes a change in physical and chemical properties..

it only works when there are 11 dimensions present..even though we can see only 3..

the other day i read about quarks and the different types of quarks..i found out wat protons and neutrons are made of...

how they have a charge or dont have a charge...i would like to talk to you abt this in detail but you dont seem to have any time at all..

BLACK HOLE

A black hole is an object — typically a collapsed star — whose gravity is so strong that its escape velocity exceeds the speed of light. Since nothing is known to exceed the speed of light, nothing can escape from a black hole.


A black hole is defined by the escape velocity that would have to be attained to escape from the gravitational pull exerted upon an object. For example, the escape velocity of earth is equal to 11 km/s. Anything that wants to escape earth's gravitational pull must go at least 11 km/s, no matter what the thing is — a rocket ship or a baseball. The escape velocity of an object depends on how compact it is; that is, the ratio of its mass to radius. A black hole is an object so compact that, within a certain distance of it, even the speed of light is not fast enough to escape.


this link below is amazing to understand black hole.


http://amazing-space.stsci.edu/resources/explorations/blackholes/lesson/index.html

My logic behind a time machine

Time machine is yet an imaginary concept of traveling in future or in past.
Example if you are walking on a road and your friend is ahead of you standing somewhere near the turn of the road whom you cannot see.
To see your friend or be with the person you have to travel fast that means u have to cover time.

this can be a probable idea behind time machine.

20th July --- Notes for IGCSE (Lectures)

Motion graphs can tell you how far a body has travelled, how fast it is moving and all the speed changes there have been.

In a speed-time graph, the velocity at any time is given by the slope of tangent to the graph at the instant. If the speed is uniform, the graph inclined straight line.

velocity -time graph gives the velocity of a moving object at different time.
The acceleration at any time is given by the slope of tangent to the graph at that time
The area enclosed by the graph between a certain time interval represent the displacement of the car travelled during that time interval. 

source
http://library.thinkquest.org/28388/Mechanics/Velacc/graph.htm

20th July --- Notes for IB (Lectures)

If you pull on a spring and stretch it, then you do work. That is because you are applying a force over a displacement. Since work is the transfer of energy, we must account for to what the energy was transferred. We say that the energy was transferred into the spring. The work becomes stored energy in the spring. The work becomes potential energy in the spring.
A spring can be stretched or compressed. The same mathematics holds for stretching as for compressing springs. We will be primarily discussing energy as it is stored in a spring when it is stretched here; however, the same physics would work for energy as it is stored in a spring when it is compressed.

The area under this graph of force vs. extension is in Joules, units of energy. 
Do not forget that units of work are units of force times units of displacement, or units of Newtons times units of meters. And units of work are units of the transfer of energy, that is, they are units of energy, or Joules.
So, the area under this graph symbolizes energy. It is the work done to stretch the spring.
Now, work is the transfer of energy. After the spring has been stretched, and work has been done, where has the energy been transferred to? We say that it has become potential energy in the spring. That is the energy has been stored in the spring. Therefore, the amount of energy symbolized by the area under the above graph is the energy that has been stored in the spring. It is the potential energy of the spring.
This area can be calculated. It is shaped like a triangle; so, its area is one half times its height times its base. We have:

Area under graph = (0.5)(F)(x)

This area is the energy stored in the spring. The symbol for the energy stored in the spring could be U_s. The U stands for potential energy and the subscript s stands for spring. So, now we have:

U_s = (0.5)(F)(x)

The spring is a linear spring where the stretching force is directly proportional to the extension, as mentioned above. This, again, can be stated as:

F = kx

Placing this substitution for F in the above formula for U_s we get:

U_s = (0.5)(kx)(x)

Removing the parentheses and noticing that x times x is x², we have:

U_s = 0.5kx²

This last formula reads: The potential energy of a spring, or the energy stored in a spring, equals one half times the spring constant times the square of the extension. This is how to calculate how much energy is stored in a spring.


Source
http://zonalandeducation.com/mstm/physics/mechanics/energy/springPotentialEnergy/springPotentialEnergy.html 

IBDP II : GROUP 4 PROJECT SUGGESTION

Some topics are here

just think on

Determine the effects of UV radiation on growth and development of plants or microorganisms.


What is the most effective substance to melt ice?  Try salt (sodium chloride), calcium chloride, cat litter, sand, rubbing alcohol, and rock salt.


What section of a city has the most pollution in the form of airborne particles?


What is the effect of a low-level electrical field on the movement of fruit flies?


Does the sun heat salt water and fresh water at the same rate?




Infrared light shows us the heat radiated by the world around us. By viewing animals in the infrared, we can actually "see" the differences between warm and cold-blooded animals. 








Sources : http://101science.com/Projects.htm
http://school.discoveryeducation.com/sciencefaircentral/Getting-Started/Investigation.html
http://www.kidsolr.com/science/page2.html

VERNIER CALIPER & MICROMETER SCREW GAUGE For IGCSE students

The parts of vernier caliper or Micrometer screw gauge is not important .

Important stuff is
How to take the readings from vernier caliper.

The first thing is to find the Least count of the Instruments

Formula is      Least Count = Minimum division on main scale
                                            ---------------------------------------------------
                                              Total No. of division on vernier scale/rotating scale
This formula is applicable for both vernier caliper and the screw gauge

To take down the readings use the formula

Total Readings of the object = Main scale reading + (Vernier scale reading x Least Count)
                                                      MSR              + (VSR     x  LC  )


The Lest count for Vernier caliper is 0.1mm or 0.01cm
                              Screw gauge  is 0.01mm or 0.001cm

FOR 8TH STANDARD ANSWER OF QUESTION NUMBER 5

check zero on your stopwatch.

Start stop watch on some recognisable point in the cycle.

stop stopwatch after 100 rotation

divide the time by number of cycles

REGARDING COMMENT

Whenever you all sent comments please mention your name and class below it
Thanks 

The Average Time

The Average time is nothing but you take multiple readings and add up all the readings and divide by the number of readings.

e.g.

1.2 s, 1.5s , 1.8s, 1.7s , 1.9 s

1.2+1.5+1.8+1.7+1.9
---------------------------  = Average Time
            5

PHYSICS STUFF FOR HIGHER LEVEL

What is Quantum Physics?

Quantum physics is a branch of science that deals with discrete, indivisible units of energy called quanta as described by the Quantum Theory. There are five main ideas represented in Quantum Theory:

1. Energy is not continuous, but comes in small but discrete units. 
2. The elementary particles behave both like particles and like waves. 
3. The movement of these particles is inherently random. 
4. It is physically impossible to know both the position and the momentum of a particle at the same time. The more precisely one is known, the less precise the measurement of the other is.
5. The atomic world is nothing like the world we live in. 

taken from http://library.thinkquest.org/3487/qp.html

THE MYSTERY

I have a strong believe that "yes their do exist ALIENS " 


Because every star is a sun and probably if few stars are exactly of the same age of our sun in that case we can expect few earth.Now the question about the people living on the different earth , whether they are equally advanced like us or not.


Even the quantum physics indicate the same.Quantum physics also talks about the parallel universe.

8TH STANDARD PRACTICE QUESTIONS

Q1. Student is given the following apparatus in order to find the density of a piece of rock.
         metre rule , pan balance , measuring cylinder that is big enough for the piece of rock 
       to fit inside and water.
       Draw a labelled diagram of apparatus from this list set up so that the student is able to 
       find the density of the stone.
       also describe the method .


Q2. A scientist needs to find the density of a sample of rock whilst down a mine. He has only a
spring balance, a measuring cylinder, some water and some thread.
(a) In the space below, draw two labelled diagrams, one to show the spring balance being
used and the other to show the measuring cylinder being used with a suitable rock
sample.

(b) The spring balance is calibrated in newtons. State how the mass of the rock sample
may be found from the reading of the spring balance.

Q3.What do u mean by
                                     i) Mass
                                    ii) Weight
Q4. What is the difference between mass and weight?

Q5. A cycle rotate approximately 100 rotation per minute. Describe carefully how a stopwatch may be used to find the time for one rotation of the cycle.

NOTE : All the above questions are based on CIE past papers .
              Try to Solve the above questions.

8TH STANDARD NOTES AND QUESTIONS ON MEASUREMENT OF LENGTH, MASS AND TIME, DENSITY , MASS AND WEIGHT

Length : It is measured in meters using a ruler

conversions    :   1m = 100cm, 1cm=10mm , 1000m = 1Km

Mass : It is measured in Kg using a pan balance/spring balance.

Conversions   : 1kg = 1000g

Time : It is measure in seconds using stopwatch / watch

conversion :   1hour = 60 Minutes , 1minute = 60 seconds

.............................................................................................................................................................

ACCURATE MEASUREMENT

The length can be measured accurately by taking more readings .

The thickness of the paper can be measured by taking a bunch of sheets and measuring it with the screw gauge.
calculating the thickness of 1 sheet by dividing the readings by no. of sheets

For example the thickness of 10 sheets are 0.012cm
then the thickness of 1 sheet is 0.0012cm

Time period of the pendulum is measured accurately by taking more number of swings.

take 10 or 20 0scillations and then calculate it for one oscillations.

..................................................................................................................................................................
MASS AND WEIGHT

Mass : Its the matter present in the object.

Weight : Its the gravitational force exterted on the object

To calculate weight
you can use the formula

W=Mg

M- mass  ,    g- acceleration due to gravity

Value of g = 10N/Kg

Mass remain constant througout the universe.

weight keep on changing according to the gravitational force exerted by the different planets
(Hope you remember that jupiter has more gravitational force, so on jupiter your weight will increase.)

...................................................................................................................................................................

DENSITY

The density of a material is defined as its mass per unit volume. The symbol of density is ρ (the Greek letter rho).

Mathematically: Density = Mass Divided By Volume

where:

ρ (rho) is the density,

m is the mass,

V is the volume.

The SI unit for density is:

§                     kilograms per cubic metre (kg/m³)

* NOTE: Significance of the density is to find the purity of the substance

For the Students to think

What is time machine?

hi to all my lovely students out there
This is the forum i created to share the vast non ending knowledge of physics.
Here not only you can can learn but also we can can share information about the different aspects of physics.
Hope all of you will definetly be a part of this initiation.
Looking forward to interesting and creative interaction

Deepak Sir
PODAR INTERNATIONAL SCHOOL