Why do transition elements show coloured complexes

we know that transition elements have vacant d orbital.Vacant d orbital consists of 5 equal energy levels .So when a light falls on it ,the unpaired electron present on it gets excited and it is transferred to the vacant d orbital of same energy level and some unpaired electron also gets transferred to higher energy level above d orbital.When it returns back to its original level it releases energy in the form of light whose wavelength is in the visible region

how to solve numericals in physics

1. Look into SI units .
2. Good sketches.
• Labeled coordinate system.
• Labeled dimensions and forces.
3. Show your thought process.
4. Follow all conventions.
5. Solve everything symbolically until the end.
6. Check answer ⇒ Does it make sense?
• Check trends.
• Check units.
7. Convert to SI, plug in to get answers.

Why do sky appears blue

a sunlight consists of seven colours (violet,indigo,blue,green,yellow,orange,red) VIBGYOR.The wavelength of the violet colour is lowest amongst this seven colour and the wavelength of the red colour is highest.Our atmosphere consists of many particles ,gases etc.We know when a particular light collides with a particle it gets scattered and the phenomnon is called scattering.This scattering is related to wavelength by the given relation.......
degree of scattering is inversely proportinal to the 4th root of wavelength.So when a sunlight comes to our earth , the violet colour of it having the lowest wavelength gets highly scattered while the red colour gets scattered to a small degree.So when a person see towards sky neither the violet nor the red colour reaches his eye only blue colour which has got medium wavelength gets scattered to some degree such that it reaches the earth and so it appears blue to us. Thus sky appears blue to us.

Photo electric effect

whenever a light of high frequency strikes a metal surface then outer electron of that metal gets ejected .This phenomenon is known as photoelectric effect and the electrons emitted is known as photoelectrons.
Let us a take a evacuated tube consisting of a two electrode anode and cathode connected to a variable voltage . when a light falls of sufficient frequecy falls on cathode electrons are emitted and it is attracted towards poitive terminal i.e anode .If both the electrodes are externally connected current flows through it and it is called photo electric current.
This photoelectric current depends on following condition.
1)if we increase the intensity of incident light i.e increase the number of photons per unit area more electron get emitted due to more collision of photons withelectron of that anode.2)If we make the anode more positive more emitted electron from cathode gets attracted towards anode, so more is the current.3)if we increase the frequency of the incident light (i.e energy) more is the energy of the emitted electron and it moves easily towards the anode due to its K.E and more is the current.
Now if we make the anode negative then ejected eletron gets repelled but the emitted electron with sufficent energy overcome this rpulsion and make its way towards anode and reach there.IF we make the anode more negative then for some particular negative voltage on this anode no electron can reach it due to repulsion.This negative voltage is known as stopping potenial

What is a Orbital Velocity?

Orbital velocity is the least velocity which should be given to any object or satellite so that it moves in its orbit.It is basically a minimum velocity given to any object so that it moves in a circular path.
If,
m= mass of the object.
R+h=height of the object or satellite.
M= mass of the earth.
v= orbital velocity.
then we know that when any object moves in a circular path there should be some forces which can provide the cetripetal force.In this case that force will be provided by the gravitational force between the earth and the object.

so,
centripetal force=gravitaional force between the earth and that object

mv^2/R+h=GMm/(R+h)^2
v^2=GM/R+h..............................1
we also know ,
mg=GMm/(R+h)^2.............................2

therefore from 1 and 2 .
v^2=g(R+h).

also from 1 we get that orbital velocity depends on its mass and its height from the earth.

Concept of Deja Vu

Deja Vu is a feeling that a particular event taking place in the present had happened in the past or had been repeated . Surveys have revealed that as much as 70% of the population have had these experiences, usually between ages 15 to 25, when the mind is still subject to noticing the change in environment.The experience is usually related to a very ordinary event, but it is so striking that it is remembered for several years afterwards.

CONCEPT:a brain consists of two parts 1)short term memory part

2)long term memory part


Short term memory part stores event occuring in the presentlong term memory part stores memory occured in the pastso while experiencing deja vu , events occuring in the present are stored in the long term memory part of the brain before the short term memory part even recieves the information and processes it and there is a fraction of second difference.So the person feels that the event in the present had happened in the past

What is a BIG BANG?

The Big Bang Theory is the dominant scientific theory about the origin of the universe. According to the big bang, the universe was created sometime between 10 billion and 20 billion years ago from a cosmic explosion that hurled matter and in all directions.
In 1927, the Belgian priest Georges Lemaître was the first to propose that the universe began with the explosion of a primeval atom. His proposal came after observing the red shift in distant nebulas by astronomers to a model of the universe based on relativity. Years later, Edwin Hubble found experimental evidence to help justify Lemaître's theory. He found that distant galaxies in every direction are going away from us with speeds proportional to their distance.
The big bang was initially suggested because it explains why distant galaxies are traveling away from us at great speeds. The theory also predicts the existence of cosmic background radiation (the glow left over from the explosion itself). The Big Bang Theory received its strongest confirmation when this radiation was discovered in 1964 by Arno Penzias and Robert Wilson, who later won the Nobel Prize for this discovery.
Although the Big Bang Theory is widely accepted, it probably will never be proved; consequentially, leaving a number of tough, unanswered questions.