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a photocell. The stopping potential is found to be V. if the distance of the light source from the cathode is reduced, explain giving reason, what change will you observe in the (i) photoelectric current (ii) stopping potential.

25.

An α particle and a proton are accelerated from the state of rest through the same potential difference V. Find the ratio of the de Broglie wavelength associated with them.

26.

If the frequency of incident radiation on a photocell is doubled for the same intensity, what changes will you observe in (i) kinetic energy of photo electrons emitted (ii) photoelectric current (iii) stopping potential? Justify your answer in each case.

27.

Show that Bohr’s second postulate, “electron revolves around the nucleus only in certain fixed orbits without radiating energy” can be explained on the basis of de Broglie hypothesis of wave nature of electron.

FIVE MARKS QUESTIONS

28.

Draw a schematic experimental arrangement used by Davisson and Germer to establish wave nature of electrons. Describe briefly how the de Broglie relation was experimentally verified in the case of electrons.

29.

Write Einstein’s photo electric equation. State clearly the salient features observed in photoelectric effect which can be explained on the basis of the above equation.

30.

The given graphs show the variation of the stopping potential V0 with the frequency ν of the incident radiations for two different photosensitive materials m1 and m2.

(i)

What are the values of work function for m1 and m2

(ii)

The values of the stopping potential for m1 and m2 for a frequency ν3 (> ν02).

If the stopping potential of the incident radiations are V1 and V2 respectively, show that the slope of the line =

ELECTROMAGNETIC WAVES

ONE MARK QUESTIONS

1.

Name the scientist who first (i) predicted the existence of EM wave. (ii) Experimentally demonstrate the existence of EM wave

2.

Write 4 properties of em waves.

3.

Write an expression for speed of em wave in free space.

4.

Write two applications of microwaves.

5.

Which part of the electromagnetic spectrum is used in operating RADAR?

6.

What is the ratio of speed of infrared and ultraviolet rays in vacuum?

7.

State modified Ampere’s circuital law.

8.

What us Maxwell’s displacement current?

TWO MARKS QUESTIONS

9.

A plane electromagnetic waves in vacuum along Y direction. Write the (i) ratio of magnitude  and (ii) direction of its electric and magnetic field vectors.

10.

Identify the following electromagnetic waves per the wavelengths given below

(i)

10-3nm

(ii)

10-3m

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