### ## PHYSICS EXPERIMENTS

discover everything from nature.....

slide 1

### ## knowledge is power

develop scientific approach...

### ## dream big

learning is continuous process....

### inspire yourself and inspire others

develop concepts....

### LEARNING BY DOING

combine experiments and theory....

## How to balance a chemical equation?

A chemical equation tells us the type of reaction between different reactants. Chemical equation gives the states of the reactants and products.  One can calculate the amount of products required for required amount of products.

To balance a chemical equation, very interesting method is algebraic expression method.

for example:  C3H8 + O2 -----> CO2  + H2O

The above reaction is to be balanced using algebraic expressions

step 1) the coefficients of Each reactants and products assumed to be a,b,c,d,...

aC3H8 + b O2 -----> c CO2  + d H2O

step 2) identify and count the number of elements on both sides of the reaction

carbon: 3a = c

hydrogen: 8a = 2d

oxygen:  2b = 2c + d

step 3) let us assume a=1, then simplify the equations for other variable values

c = 3,     2d = 8   then d = 4             if d=4 and c =3 then 2b=6 + 4 = 10, b=5

step 4) write the chemical equation using the variable values

C3H8 + 5O2 ---> 3CO2  + 4 H2O

step 5) count the number of atoms on both sides

carbon atoms  = 3
hydrogen atoms = 8
oxygen atoms = 10

step 6) we conclude that the equation is said to be balanced.

## Stephen William Hawking....great Mathematician, Physicist

Prof. Stephen william Hawking was born on 8th Jan. 1942, in Oxford, England.  Stephen studied at St. Albans School.  Stephen was awarded Ph.D. titled "properties of Expanding Universe" in 1965.  Stephen William Hawking  was an English theoretical Physicist and Cosmlogist.

### Important Concept from Stephen William Hawking.......

This is the black body radiation which is supposed to be released by blackholes due to Quantum effects.  This leads to black hole evaporation, the meaning is, Hawking radiation reduces the mass and energy of blackholes.

AWARDS :

1. The Adams Prize: The prize is named after the mathematician "John Conch Adams"

2. Eddington Medal: Royal Astronomical society awards the Eddington Medal.

3. Fundamental Physics Prize: It is awarded by Fundamental Physics Prize Foundation

### TOP BOOKS WRITTEN BY STEPHEN WILLIAM HAWKING:

"A Briefer history of time" a famous book written by Stephen Hawking.  A Briefer history of time books gives explanation on all the forces of physics.

Another book - "The Universe in a Nutshell".

Stephen is a fellow of the Royal society and he is a member of the US National academy of Science.

## What is a Lens?

A transparent medium bounded by two surfaces, at least one of the surface should be a curved, is said to be a lens and it is said to be THIN LENS, When there is a small gap between the two surfaces or lenses where the thickness are much less and considered negligible in comparison to the radius of curvature.

When a lens of refractive index n2 is placed in the medium of refractive index n1, and the radii of curvatures of lens are R1 and R2, then we can write

( n1/v)-(n1/u)  =  (n2-n1)[1/R1  -  1/R2]

dividing the equation by n1,

we get,   1/v  -  1/u  =  (n2/n1  - 1)[1/R1 - 1/R2]

when the object is at infinity, u = infinity,  and then the image distance v = f, then

lens maker's formula is    1/f = (n2/n1  - 1)[1/R1 - 1/R2]

1/f =(n-1)[1/R1 - 1/R2]

LIMITATIONS OF LENS MAKER'S FORMULA :

- the lens should be thin to consider above formula and the medium is same on either side of the lens.

sign conventions:

for convex lens:

R1 is positive,  R2 is negative and f is positive

for concave lens:

R1 is negative, R2 is positive and f is negative

### PROBLEMS USING LENS FORMULA:

1. An object is placed at 8 cm from a lens of  focal length 15 cm, then calculate the image distance and determine whether the image is real or virtual.

2. A student using a lens of focal length -15cm, and object is placed at 20 cm from it, then calculate how far the image is from the lens and find out the magnification.  Conclude whether the image is real or virtual.

3. Calculate the image distance and determine whether the image is real or virtual when an object is placed at 20 cm, from a lens of negative focal length -10cm.

## Tuesday, 6 March 2018

### What is net neutrality?

NET NEUTRALITY.........

## PROBLEMS IN PHYSICS - REFLECTION AT CURVED SURFACES

PROBLEM 1:

Where is the image formed when 8 cm tall object is placed at 20 cm. in front of a concave mirror with focal length 5 cm.  Find out the size of the image also.

PROBLEM 2:

A 10 cm tall object is placed in front of a convex mirror of focal length 15 cm, Find out the image distance and write its characteristics .

PROBLEM 3:

10 cm focal length concave mirror is placed at 40 cm, from a wall.  Calculate the object distance such that its image is formed on the wall.

PROBLEM 4:

In front of 15 cm focal length concave mirror, an object is placed at 30 cm, if the object is displaced through 10 cm towards mirror, calculate by how much distance the image is displaced?

PROBLEM 5:

The image is formed behind the mirror, at a distance of 10 cm, when an object is placed at 20 cm in front of it.  Identify the type of mirror used and also calculate the focal length.