MVN Pr actice test-1 C-1

SECTION-A
1. Which of the following statement is not correct about the characteristics of cathode rays?
(A) They start from the cathode and move towards the anode.
(B) They travel in straight line in the absence of an external electrical or magnetic field.
(C) Characteristics of cathode rays do not depend upon the material of electrodes in cathode ray
tube.
(D) Characteristics of cathode rays depend upon the nature of gas present in the cathode ray tube.

2. Which of the following is responsible to rule out the existence of definite paths or trajectories of
electrons?
(A) Pauli’s exclusion principle.
(B) Heisenberg’s uncertainty principle.
(C) Hund’s rule of maximum multiplicity.
(D) Aufbau principle

3 Which of the following statements concerning the quantum numbers are correct?
(i) Angular quantum number determines the three dimensional shape of the orbital.
(ii) The principal quantum number determines the orientation and energy of the orbital.
(iii) Magnetic quantum number determines the size of the orbital.
(iv) Spin quantum number of an electron determines the orientation of the spin of electron
relative to the chosen axis
Choose the correct option :
(A) i, ii, iii (B) i, ii, iii, iv (C) i, ii (D) iii, iv

4. Assertion (A) : Black body is an ideal body that emits and absorbs radiations of all frequencies.
Reason (R) : The frequency of radiation emitted by a body goes from a lower frequency to higher
frequency with an increase in temperature.
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is not the explanation of A.
(C) A is true and R is false.
(D) Both A and R are false.
5. Assertion (A) : It is impossible to determine the exact position and exact momentum of an
electron simultaneously.
Reason (R) : The path of an electron in an atom is clearly defined.
(A)Both A and R are true and R is the correct explanation of A.
(B)Both A and R are true and R is not the correct explanation of A.
(C) A is true and R is false.
(D) Both A and R are false.

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6. When green light is incident on a certain metal surface electrons are emitted but no
electrons are emitted by yellow light. If red light is incident on the same metal surface
then :

(A) more energetic electrons will be emitted.

(B) less energetic electrons will be emitted.

(C) emission of electrons will depend on the intensity of light.

(D) no electrons will be emitted.

7. Which of the following graphs is representing correctly the relation between

photoelectron energy and wavelength of incident light :

(A) (B)

(C) (D)

8. Identify the incorrect statement from the following.

(A) All the five 4d orbitals have shapes similar to the respective orbitals.
(B) In an atom, all the five 3d orbitals are equal in energy in free state.
(C) The shapes of dxy, dxz ,dzy and orbitals are similar to each other; and dx2- y2 , dz2and are similar
to each other.
(D) All the five orbitals 5d are different in size when compared to the respective 4d orbitals.
9. The maximum velocity of an electron emitted by light of wavelength incident on the
surface of a metal of work function is :

1/ 2 1/ 2 1/ 2
(hc − ) 2(hc − ) 2(hc − ) 2(h − )
(A) (B) (C) (D)
m m m m

10. A photosensitive metallic surface has work function, hυ0, If photons of energy 2hυ0 fall
on this surface, the electrons come out with a maximum velocity of 4 × 106 m/s. When
the photon energy is increased to 5hυ0, then maximum velocity of photo electrons will
be :

(A) 2 × 107 m/s (B) 2 × 106 m/s (C) 8 × 106 m/s (D) 8 × 105 m/s

11. The work functions for metals A, B and C are respectively 1.92eV, 2.0eV and
5eV.According to Einstein's equation, the metals which will emit photoelectrons for a
radiation of wave length 4100 Å is/are:

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(A) None (B) A only (C) A and B only (D) All the three

12. If J be the angular momentum of an electron in an orbit then orbit radius according to Bohr's
theory is equal to :
(A) J/p (B) J/v (C) J/m (D) J/2

13. According the Bohr model the radius (r) and velocity (v) of an electron varies as :
(A) r increases, v decreases. (B) r and v both increases,
(C) r and v both decrease. (D) r decreases, v increases

14. A single electron orbits a stationary nucleus of charge + Ze, where Z is a constant. It requires
47.2 eV to excited electron from second Bohr's orbit to third Bohr orbit. Find the value of Z :

(A) 2 (B) 5 (C) 3 (D) 4

15. Ionisation potential of Hydrogen atom is 13.6eV. Hydrogen atoms in the ground state
are excited by monochromatic radiation of photon energy 12.1 eV. The spectral lines
emitted by hydrogen atoms according to Bohr's theory will be :
(A) one (B) two (C) three (D) four

16. When an hydrogen atom is excited from ground state to an higher state:
(A) both kinetic and potential energy decreases.
(B) both kinetic and potential energy increases.
(C) potential energy increases and kinetic energy decreases.
(D) potential energy decreases and kinetic energy increases.

17. Which of the following options represent the correct graph for photoelectrons?

(A) (B)

(C) Both of the above (D) None of these

18. Light of wavelength strikes a metal surface with intensity X and the metal emits electrons per
second of average energy Z. If X is halved, the and Z will be:

(A) will be halved, Z will be doubled

(B) will be doubled, Z will be halved

(C) will be halved & Z will remain same

(D) will remain the same and Z will be halved

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19. The maximum number of electrons in a subsbell (l):

(A) decreases with increase in l.

(B) increases with increase in l.

(C) increases with decrease in l,

(D) is independent of l,

20. There is transition from n = 1 to n = 2 and then n = 2 to n = 3. Thus,

(A) E values as well as frequencies are additive
(B) wavelengths as well as frequencies are additive
(C) E as well as wavelengths are additive
(D) all the parameters, ( E, frequency and wavelength) are additive
SECTION-B
21. Maximum number of electrons that can be accommodated in shell with n = 4 are _____

22. The Balmer series in the hydrogen spectrum corresponds to the transition from n1=2 to
n2=3,4,.......... This series lies in the visible region. Calculate the wave number of line associated
with the transition in Balmer series when the electron moves to n = 4 orbit. (RH = 109677 cm–1)
23. The work function of sodium metal is 4.41 × 10–19 J. If the photons of wavelength 300 nm are
incident on the metal, the kinetic energy of the ejected electrons will be ________ × 10–21 J.

(h = 6.63 × 10–34 Js; c = 3 × 108 m/s)

24. Given that the radius of the first Bohr orbit of hydrogen atom is 53 pm, the radius of its third Bohr
orbit is __________ pm. (Round off to the nearest integer)

25. The electron of a hydrogen atom is in its nth Bohr orbit having de Broglie wavelength of
13.4 Å. The value of n is ______ (rounded up to the nearest integer).
[Radius of nth Bohr orbit = 0.53n2 Å, π = 3.14]

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