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Question .1. What are , and radiations composed of?

Question .2. What is thermionic emission? Name two factors on which thermionic
emission depends.

Question .3. An alpha particle absorbs an electron. What does it change to?

Question.4. (i) A thorium isotope 223Th90 undergoes an decay and changes into
Radium. What is the atomic number and mass number of the radium produced?
(ii) If the radium undergoes a further disintegration and emits two beta particles,
represent this reaction in the form of an equation.
(iii) What is the source of energy released during the decay?

Question .5. An atomic nucleus denoted by AXZ emits an alpha particle. Write an
equation to show the formation of the daughter product.

Question .6. A radioactive nucleus AXZ first emits a beta particle and then an alpha
particle and the resulting nucleus is represented by PYQ. What are the values of P
and Q in terms of A and Z?

Question .7. What is radioactivity ?

Question .8. A radioactive substance is oxidized. What change would you expect
to take place in the nature of the radioactivity? Give a reason for your answer.

Question .9. Explain what changes take place within the nuclei, when beta
particles are emitted by a radioactive substance?

Question .10. Name the particles given out during radioactive decay.

Question .11. Show by equations, the effect on the proton number Z and the mass
number A of the parent nucleus brought about by the two types of radioactive

Question .12.

(i) 27Mg12 emits a beta particle and is transformed into aluminium. Write the mass
number and the atomic number of aluminium.
(ii) Aluminium emits a gama ray. What is the resulting nucleus?

Question .13. Which radiation or particle from radioactive decay produces

maximum biological damage?

Question .14. State three precautions that must be taken while handling a
radioactive source.

Question .15. An element X changes into another element Y with the emission of
beta particle. Write down the equation showing the changes in the nucleus. Take
the proton number of X as Z and A respectively.

Question .16. Describe briefly, two properties each of alpha and gamma

Question .17. A mass of lead is embedded in a block of aluminium. Radiations

from a radioactive source incident on the side of the block produce a shadow on
a fluorescent screen placed beyond the block. The shadow of aluminium is faint
but the shadow of lead is dark. Give reason for this difference.

Question .18. The isotope of uranium 238U92 decay by alpha emission to an isotope
of thorium (Th). The thorium isotope decay by beta emission to an isotope of
Protactinium (Pa). Write down the equations to represent these two nuclear

Question .19. Define the term work function of a metal.

Question .20. Mention two common properties of gamma radiations and visible

Question .21. State one use of radioisotopes.

Question .22. Why are materials of low work function preferred as thermionic
cathode materials?

Question .23. A certain radioactive nucleus emits a particle that leaves its mass
unchanged but increases its atomic number by one. Identify the particle and write
its symbol.

Question .24. (i) Define thermionic emission.

(ii) Mention one use of thermionic emission.
(iii) Name a substance which is a good thermionic emitter.

Question .25. State three properties that are common to and shown by both beta
rays and cathode rays.

Question .26. What will an alpha particle change into when it absorbs :
(i) One electron
(ii) Two electrons?

Question .27. Mention two important properties of a metal that make it a good
thermionic emitter.

Answer :

Question .28. (i) What happens to the atomic number of an element when it emits:
(1). an alpha particle and
(2). a beta particle.
(ii) Explain why alpha and beta particles are deflected in an electric or a magnetic
field but gamma rays are not deflected in such a field.