Q13 of 26 Page 1

Sketch the graphs showing variation of stopping potential with frequency of incident radiations for two photosensitive materials A and B having threshold frequencies .

(i) In which case is the stopping potential more and why?


(ii) Does the slope of the graph depend on the nature of the material used? Explain.

(i) The stopping potential has a linear relation with the frequency of incident radiation. It increases linearly with the increase in frequency of incident radiation . Therefore, the stopping potential of metal A is more than that of metal B .νB


(ii)


(ii) No, the slope of the graph does not depend on the nature of the material used. Since, the slope of the graph tells us the value of h/e which is constant for both the materials.


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11

Define an equipotential surface. Draw equipotential surfaces:

(i) in the case of a single point charge and


(ii) in a constant electric field in Z-direction. Why the equipotential surfaces about a single charge are not equidistant?


(iii) Can electric field exist tangential to an equipotential surface? Give reason.

 12

(i) State law of Malus.

(ii) Draw a graph showing the variation of intensity (I) of polarised light transmitted by an analyser with an angle (θ) between polariser and analyser.


(iii) What is the value of the refractive index of a medium of polarising angle 60°?

 14

(a) Write the basic nuclear process involved in the emission of in a symbolic form, by a radioactive nucleus.

(b) In the reactions given below:


(i)


(ii)


Find the values of x, y, and z and a, b and c.

 15

(i) Derive an expression for drift velocity of free electrons.

(ii) How does drift velocity of electrons in a metallic conductor vary with increase in temperature? Explain.