10 Question-answer on cathode rays and positive rays
1. Cathode rays are made to pass between the poles of magnet perpendicular to axis, the effect of the magnetic field is:
(a) To increase the velocity of rays
(b) To deflect them towards the north pole
(c) To deflect them towards the south pole
(d) To deflect them upwards above the plane of paper
Ans: ( d)
2. The mass of a proton is 1836 times that of an electron. An electron and a proton are projected into a uniform electric field in a direction perpendicular to the field with equal initial kinetic energies. Then
(a) The electron trajectory is less curved than the proton trajectory
(b) The proton trajectory is less curved than the proton trajectory
(c) Both trajectories are equally curved
(d) Both trajectories will be straight
Ans: (c)
3. The two parabolas obtained by Thomson for neon are due to
(a) Presence of impurities
(b) Two types of atoms with same atomic number but different mass number
(c) Two types of atoms with same mass number but different charge number
(d) Two types of atoms in different energy states
Ans: (b)
4. Cathode ray tube is a part of
(a) Compound microscope
(b) A radio receiver
(c) A television set
(d) A van de Graaf generator.
Ans: (c)
5. A strong argument for the particle nature of cathode rays is that they
(a) Produce fluorescence
(b) Travel through vacuum
(c) Get deflected by electric and magnetic fields
(d) To cast shadow.
Ans: ( c)
6. The mean free path of the electrons in a discharge tube is 15 cm. the length of the tube is 10 cm only. Then length of Crooke’s dark space is:
(a) 5 cm
(b) 10 cm
(c) 15 cm
(d) 25 cm
Ans: (b)
7. The momentum of a charged particle moving in a perpendicular magnetic field depends on
(a) Its charge
(b) The strength of magnetic field
(c) Radius of its path
(d) All of the above.
Ans: (d)
8. Cathode rays is
(a) A beam of atoms moving towards cathode
(b) Electromagnetic waves
(c) A beam of negatively charged ions moving towards anode
(d) A beam of electrons emitted by cathode.
Ans: ( d)
9. The specific charge for positive rays is much less than that for cathode rays. This is because
(a) Masses of positive rays much larger
(b) Charge on positive ray is less
(c) Positive rays are positively charged
(d) Experimental method is wrong.
Ans: (a)
10. In fluorescence there is:
(a) Increase in wavelength
(b) Decrease in wavelength
(c) No change in wavelength
(d) Both increase and decrease in wavelength
Ans: ( a)