diffraction

What happens when squirrels do not move.

Stationary state and squirrels !

Okay so the squirrel isn’t moving around so much, giving a fuzzy image. We can call the instant during which the squirrel wasn’t moving akin to a “gross” stationary state.

But why is the railing of window fuzzy? It isn’t moving !

Diffraction.

Due to diffraction enough light is coming from the other side of the iron bar, to enable us to see whats there. That quadrangle is diffracting the light. But why its fuzzy?

Diffraction is by its own very nature even though purely classical in many sense, fuzzy towards energy if time window is small. [due to energy vs time uncertainty]

That is, full energy cycle isn’t available, because a small time window is chosen. If you time-lapse the photograph, diffraction will become quite insignificant. Although it might still be there depending on details.

I.S.C. Board Question Paper. Physics, Class XII – 2009 ( C.I.S.C.E. )

Question 1 
Answer all question briefly and to the point.

(i)
Explain the statement ‘relative permittivity of water is 81’.

(ii)
Draw (at least three) electric lines of force due to an electric dipole.

(iii)
Find the value of resistance X in the circuit below so that the junction M and N are at the same potential.

(ix)
A ray LM of monochromatic light incident normally on one refracting surface AB of a regular glass prism ABC emerges in air from the adjacent surface AC as shown in Figure. Calculate the refractive index of the material of the prism.

SECTION A
(Answer any two questions)

Question 2 
(a)
With the help of a labeled diagram, obtain an expression for the electric field intensity ‘E’ at a point P in broad side position (i.e. equatorial plane) of an electric dipole.

Question 3
(c)
(i) State any two differences between a moving coil galvanometer and a tangent galvanometer.

(ii) What is the use of a Cyclotron?

SECTION C
(Answer any two questions)

Question 8
(a)
Electrons, initially at rest, are passed through a potential difference of 2 kV. Calculate their:

(i) Final velocity and

(ii) de Broglie wavelength