24.

Calculate the longest and shortest wavelength in the Blamer series of hydrogen spectrum. Given R= 1.0987 x 107/m.

25.

Calculate the binding energy per nucleon in the case of . Given mass of proton = 1.007825 amu. Mass of neutron = 1.00865 amu, mass of the nucleus is 55.934939 amu.

26.

State and explain the laws of radioactive disintegration and hence define disintegration constant and half life period. Establish the relation between them.

27.

Plot a graph between mass number and average binding energy per nucleon and hence explain the energy released in the process of nuclear fission and fusion.

FIVE MARKS QUESTIONS

28.

State the basic postulates Bohr’s atom model. Obtain the relation for the frequency of spectral lines emitted from hydrogen atom.

29.

Which of the following radiations are α β and γ rays.

a.

Similar to X rays

b.

Easily absorbed by the matter

c.

Travel with greatest speed.

d.

Similar in nature to cathode rays

After two hours 1/16 th of initial amount of certain radioactive isotope remains undecayed. What is the half life of the isotope?

30.

If 200 MeV energy is released in the fission of single nucleus of, how many fissions must occur to produce a power of 1 kW. What are the functions of moderator and control rods in nuclear reactor? Give an example for each.

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DUAL NATURE OF MATTER AND RADIATION

ONE MARK QUESTIONS

1.

What is the stopping potential applied to a photocell if the maximum KE of the photoelectron is 5eV?

Hint: eVo=5eV

2.

If the intensity of radiation in a photocell is increased how does the stopping potential vary?

Unchanged

3.

Two metals A and B have work function 2eV and 4 eV respectively. Which has lower threshold wavelength?

Hint: λ 1/W0

4.

What is photoelectric effect?

5.

De Broglie wavelength associated with an electron accelerated through a potential difference V is λ. What will be the wave length when potential is increased to 4V?

Hint: λ = h/2meV

6.

Which of the following radiations will be more effective for electron emission from the surface of zinc?

Microwaves, infrared,ultraviolet

Hint: UV has max freq

7.

An electron and an α particle and a proton has the same KE. Which one has the shortest wavelength?

Hint: λ i/√ m

8.

With what purpose Davisson Germer experiment performed?

TWO MARKS QUESTIONS

9.

For a photosensitive surface threshold wavelength is λ 0. Does photoemission occur if the wavelength of radiation is (a) more than λ 0 (b) less than λ 0. Justify.

Hint: for emission EW0

10.

Explain the terms threshold frequency and stopping potential.

11.

Draw a graph showing the variation of stopping potential with frequency of radiation. How can the value of Planck’s constant be determined from the graph?

Hint: h= slope of the graph.

12.

Why de Broglie wave associated with a moving football is not visible?