NEET Physics Matter Waves Cathode and Positive Rays MCQs Set 01

Question: A strong argument for the particle nature of cathode rays is that they
a) get deflected by electric and magnetic fields
b) cast shadow
c) travel through vacuum
d) produce fluoroscence
Answer: get deflected by electric and magnetic fields

Question: In an electron gun the control grid is given a negative potential relative to cathode in order to
a) repel electrons and thus to control the number of electrons passing through it
b) to select electrons of same velocity and to converge them along the axis
c) to decrease the kinetic energy of electrons
d) decelerate electrons
Answer: repel electrons and thus to control the number of electrons passing through it

Question: When the speed of electrons increase, then the value of its specific charge
a) decreases
b) increases
c) ramains unchanged
d) increases upto some velocity and then begins to decrease
Answer: decreases

Question: The specific charge for cathode rays is
a) constant
b) variable
c) depend upon the material of the cathode
d) depend upon the nature of gas in the discharge tube
Answer: constant

Question: particle with rest mass m₀ is moving with speed of light c. The de-Broglie wavelength associated with it will be
a) zero
b) m₀ c/h
c) Both
d) None of these
Answer: zero

Question: If a photon and an electron have same de-Broglie wavelength, then

a) electron has more K.E. than proton
b) both have same velocity
c) proton has more K.E. than electron
d) both have same kinetic energy
Answer: electron has more K.E. than proton

Question: Cathode rays and canal rays produced in a certain discharge tube are deflected in the same direction if

a) a magnetic field is applied normally
b) an electric field is applied normally
c) an electrin field is applied tangentially
d) a magnetic field is applied tangentially
Answer:  a magnetic field is applied normally

Question:  If the momentum of electron is changed by P, then the de Broglie wavelength associated with it changes by 0.5%. The initial momentum of electron will be

a) 200 P
b) 400 P
c) 100 P
d) 300 P
Answer: 200 P

Question: Cathode rays are made to pass between the poles of a magnet perpendicular to axis, the effect of the magnetic field is

a) to deflect them upwards above the plane of paper
b) to deflect them towards the south pole
c) to deflect them towards the north pole
d) to increase the velocity of rays
Answer: to deflect them upwards above the plane of paper

Question: If the kinetic energy of the particle is increased to 16 times its previous value, the percentage change in the de-Broglie wavelength of the particle is :
a) 75
b) 60
c) 50
d) 25
Answer:  75