## Class XII, ICSE exam questions, Physics, Updated Version 2

Question 6 [2+3+2]

Obtain an expression for the Nuclear Size of an atom by solving for distance of closest approach (r) which is also known as Impact Parameter (say l). Use an incoming alpha-particle of mass mα and charge q that’s deflected by the presence of a nucleus of atomic number Z to obtain l. Now replace the variables by some numerical: mα = 6.8×10-27kg, e = 1.6 x 10-19 coul, Z=14, and vα= 2.0×107 m/s. Express the answer in Femto-meters.

Question 7 [3+4]

A proton has a radius R and the charge Q is uniformly distributed. Use Bohr’s atomic energy level formula for the 1st excited state {n=2} energy of the Hydrogen-atom.

## Class XII, CBSE exam questions, Physics

Electrostatics

6. State how density of electric lines of force is related to the Electric Field Vector intensity E. Also mention another three properties of the lines of forces.

7. Write the vector expression for Coulomb’s law and state 3 forces that are conservative forces by nature.

8. What happens to the charge on a conducting shell? What happens to lines of forces when a conducting shell is present in the path of the lines of forces?

## Class XII, ICSE exam questions, Physics.

Question 1

(a) In an electric dipole, how is the direction of the dipole vector defined?

(b) What’s the Electric Potential of a Dipole Vector in the vertical direction to it?

(c) Say if this is correct or incorrect: “Between an alpha-particle and a proton the alpha particle has more electrostatics potential energy in an electrostatics potential of 100 volt.”?

(d) Give example of 3 conservative forces and state if this is true or not-true: “The work done in a conservative force field during a circular voyage is proportional to the amount of charge on the voyage”?

## ତ୍ରିଭୁଜ ଏବଂ ଖଣ୍ଡବିଦ୍ୟା ନିୟମ !

ପ୍ରଥମତଃ ସେ ଏକ ଆଇନ୍-ଷ୍ଟେଇନିଆନ୍ ବିଦ୍ଧି ରେ ଏବଂ ତା ପରେ ଏକ ସ୍ରୋଡିଂଜର୍ ବିଦ୍ଧି ରେ ସଠିକ୍ ନ ଥିଲେ ! ଆମର ବିଶ୍ବ ର ଭୌତିକ ସଂରଚନା ରେ ଅନେକ ଅଖାପ କିଂବା ଅଣ-ସଂବନ୍ଧି ଅମେଳ ଦୃଶ ହେଲେ ଯାହା ଭୌତିକ ପ୍ରବୃତ୍ତୀ ର ରହସ୍ୟପୁର୍ଣ୍ଣ ଚରିତ୍ରବତ୍ତା କୁ ସୁଚାଉ ଥିଲେ, ଯଥା ଘନ-ଶରୀର ପ୍ରଭା-ବ୍ୟାପକତା (black-body spectrum) ! ଏହି ପ୍ରଭା-ବ୍ୟାପକତା ରେ ନିମ୍ନ ଶକ୍ତୀ ସ୍ତର ର ଅବସ୍ଥାନ କରିବା ସୁଚାଏ ଯେ ସେଥିରେ କଣିକାଖଣ୍ଡ ପ୍ରବୃତ୍ତୀ ଥାଏ ଏବଂ ଉଚ୍ଚ ଶକ୍ତୀ ସ୍ତର ର ଅବସ୍ଥାନ କରିବାସୁଚାଏ ଯେ ସେଥିରେ ତରଂଗ ବା ଅନେକର୍ଣ୍ଣ-କଣିକାଖଣ୍ଡ ପ୍ରବୃତ୍ତୀ ଥାଏ ! ସମ୍ପୁର୍ଣ୍ଣ-ସତ୍ତା ଅର୍ଥ ରେ ଏ ସବୁ ରେ ତରଂଗ-କଣିକାଖଣ୍ଡ ପ୍ରବୃତ୍ତୀ ଅବସ୍ଥାନ କରେ ! ଏ ସମସ୍ତ ଜ୍ଞାନ “ସଠିକତା ର ଅଭାବ” ମଧ୍ୟ ରେ ଲୁଚି ରହି ଥିଲା ଠିକ୍ ଏପରି ଏକ ମହାନତା ଯେମିତିକି “ତୁମର ଯୋତା” ! ଯୋତା-ପ୍ରବନ୍ଧକ ର ବିଦ୍ଧି-ନିଦେଶ କୁ ପବିତ୍ର-ସଂକେତ ମନେ କରିବା କୁ ମନା କରିଦେବା ଦ୍ବାରା ବସ୍ତୁ-ବିଦ୍ ମାନେ ଅନାଦୃତ ବିଧୌତ-ମୁଣି ହେଇ ଗଲେ ନାଃହିଂ ବରଂଚ ଏହା ଦ୍ବାରା ସେମାନେ ନବକଳ୍ପିତ ଜ୍ଞାନ ର ସମ୍ଭାଷଣ କୁ ଆଦୃତ କରାଇଲେ ! ତଥା ତୁମେ ସୁରକ୍ଷିତ ମଣି କହି ପାରିବ ଯେ ସମସ୍ତ ଖଣ୍ଡଚଳ ନିୟମ ଏବଂ ସାଧାରଣ-ଆପେକ୍ଷିକତା ତଥା ନିର୍ଦିଷ୍ଟ ଆପେକ୍ଷିକତା ର ଦୁନିଆ ଯୋତା ର ଧାର ମଧ୍ୟ ରେ ଲୁଚ୍ଚାୟିତ ଥିଲା.

## You know Einstein was very clever. (Information Theory in Physics )

Then he goes S = Int{Ldt}, action is the total amount of specified definitions of energy over all of time, and action is a kind of information if we are dealing with a statistical system of L {energy} because Energy is not known precisely, or rather action is not, this fact is brought in by saying the time is an information or a PLAN, because things are not known precisely although depend on other well defined factors. Then he sees that since interactions of different chunks of Energy with each other which are not known very precisely gives rise to heat or temperature, temperature here serves as information or PLAN. Then this is still called S, akin to action because S again is information or imprecise or statistical. Then they call it Entropy. {Perhaps for INTERnal-Energy = Intropy} But this other factor temperature also is denoted by same initial T. Since T has to be a fundamental parameter as are Energy and Entropy it can go anywhere, in denominator or numerator and sitting below sometimes feels good so they give T the chance to do that. Its better to heat from below. Heat works that way. But Time T sits on top, see: S = Int{Ldt}.

## Triangles and Particle Physics !

Phase Space.

When we deal with what we call particle physics, we always have to bring into discussion; whats a phase space. Its the most basic thing to do, in that involvement. Its like each time we make pizza we have to think of whats the dough and whats the topping. At-least the theoretical and experimental particle physicists would think so.

Whats phase space? How is it that the special relativity was hidden into a small angle?

Lets first talk phase space.

Phase space literally means a space of angles. A phase is an angle. But what is the angle? The angle that gives us the direction of momentum. And the magnitude of the momentum is directly connected to the energy.