Practice Test - Dual Nature of matter, Atom-molecular nuclei, Semi-conductors & Communication Notes | EduRev

: Practice Test - Dual Nature of matter, Atom-molecular nuclei, Semi-conductors & Communication Notes | EduRev

 Page 1


                                   [1] 
 
 
 
(Dual Nature of matter, Atom-molecular nuclei, Semi-conductors & 
Communication)  
1. An electron and a proton are injected into a 
uniform electric field at right angle to the field 
with the same kinetic energy. What is the nature 
of their trajectories? 
(a) Electron trajectory is more curved than the 
proton trajectory  
(b)  Electron trajectory is less curved than the 
proton trajectory 
(c) Both trajectories are equally curved  
(d) Both trajectories are straight lines. 
2. When a beam of accelerated electrons hits a target, 
continuous X- ray spectrum is emitted from the 
target. Which one of the following wavelength is 
absent  in the X-rays tube is operated at 40,000 V?  
(a) 1.5Å (b)  0.5 Å 
(c) 0.25 Å (d) 1.0 Å 
3. Ultraviolet radiation of 6.2 eV falls on an 
aluminium surface (work function 4.2 eV). The 
kinetic energy in joule of the fastest electron 
emitted is approximately 
(a) 3 × 10
-
21  
(b)  3 × 10
-
19
 
(c) 3 × 10
-
17 
(d) 3 × 10
-
15
 
4. T is the half life period and T
a
 is the average life 
of a radioactive substance. Which of the following 
statement is correct ? 
(a) T > T
a
  
(b)  T is about 69% of T
a 
(c) T is inversely proportional to T
a
  
(d) T and T
a
 both are directly proportional to 
radioactive decay constant. 
5. Bi has a half life of 5 days. What time is taken by 
(7/8)th part of the sample to decay ?  
(a) 3.4 days (b)  10 days 
(c) 15 days (d) 20 days. 
6. From the following equations pick out the 
possible nuclear fusion reaction 
(a) 6
C
13
 + 
1
H
1
 ? 
6
C
14
 + 4.3 MeV  
(b) 
6
C
12
 + 
1
H
1
 ? 
7
N
13
 + 2 MeV  
(c) 
7
N
14
 + 
1
H
1
 ? 
8
O
16
 + 7.3 MeV  
(d) 
92
U
235
 + 
0
n
1
 ? 
54
Xe
140
 + 
38
Sr
94
 + 2(
0
n
1
) + ? + 
200 MeV 
7. The stopping potential as a function of frequency 
of incident radiation is 
plotted for two 
different photoelectric 
surfaces A  and B. The 
graphs shows that the 
work function of A is 
(a) greater than that 
of B 
(b) smaller than that of B 
(c) same as that of B 
(d) such that no comparison can be done from 
given graphs 
8. The minimum wavelength of X-rays produced by 
accelerating potential V is ?. What will be the 
minimum wavelength, when the accelerating 
potential is 2 V. 
(a) 2 ? (b) 2 ? 
(c) ? 2 (d) ?/2 
9. The relation between  half life T
1/2
 of a radioactive 
sample and its mean life ? is 
(a) T
1/2
 = 0.693 t (b) t = 0.693 T
1/2
 
(c) t = T
1/2 
(d) t = 2.718 T
1/2 
10. According to Bohr’s theory the radius of electron 
in an orbit described by principal quantum 
number n and atomic number Z is proportional to 
(a) Z
2
n
2 
(b) Z
2
/n
2
 
(c) (Z
2
/n) (d) (n
2
/Z). 
11. A transistor is preferable to triode valve because it   
(a) can withstand larger changes in temperature  
(b) has higher input impedance  
(c) can handle larger powers   
(d) does not require a heater  
12. What is the value of A . A in Boolean algebra : 
(a) 0 (b) 1  
(c) A (d) A 
13. When NPN transistor is used as an amplifier then   
(a) electrons move from base to collector   
(b) holes move from emitter to base   
(c) electrons move from collector to base  
(d) holes move from base to emitter  
14. In p -type semiconductor :  
(a) major current carriers are electrons   
(b) major current carriers are mobile negative 
ions   
(c) major current carriers are mobile holes   
(d) the number of mobile holes exceeds the 
number of acceptors  
15. The diffusion current in a P -N junction is :  
(a) from n -side to p -side   
(b) from p -side & n -side   
(c) from n -side to p -side, if forward biased  
(d) from p -side to n -side, if reverse biased  
16. n -type germanium is obtained on doping intrinsic 
germanium with :  
Page 2


                                   [1] 
 
 
 
(Dual Nature of matter, Atom-molecular nuclei, Semi-conductors & 
Communication)  
1. An electron and a proton are injected into a 
uniform electric field at right angle to the field 
with the same kinetic energy. What is the nature 
of their trajectories? 
(a) Electron trajectory is more curved than the 
proton trajectory  
(b)  Electron trajectory is less curved than the 
proton trajectory 
(c) Both trajectories are equally curved  
(d) Both trajectories are straight lines. 
2. When a beam of accelerated electrons hits a target, 
continuous X- ray spectrum is emitted from the 
target. Which one of the following wavelength is 
absent  in the X-rays tube is operated at 40,000 V?  
(a) 1.5Å (b)  0.5 Å 
(c) 0.25 Å (d) 1.0 Å 
3. Ultraviolet radiation of 6.2 eV falls on an 
aluminium surface (work function 4.2 eV). The 
kinetic energy in joule of the fastest electron 
emitted is approximately 
(a) 3 × 10
-
21  
(b)  3 × 10
-
19
 
(c) 3 × 10
-
17 
(d) 3 × 10
-
15
 
4. T is the half life period and T
a
 is the average life 
of a radioactive substance. Which of the following 
statement is correct ? 
(a) T > T
a
  
(b)  T is about 69% of T
a 
(c) T is inversely proportional to T
a
  
(d) T and T
a
 both are directly proportional to 
radioactive decay constant. 
5. Bi has a half life of 5 days. What time is taken by 
(7/8)th part of the sample to decay ?  
(a) 3.4 days (b)  10 days 
(c) 15 days (d) 20 days. 
6. From the following equations pick out the 
possible nuclear fusion reaction 
(a) 6
C
13
 + 
1
H
1
 ? 
6
C
14
 + 4.3 MeV  
(b) 
6
C
12
 + 
1
H
1
 ? 
7
N
13
 + 2 MeV  
(c) 
7
N
14
 + 
1
H
1
 ? 
8
O
16
 + 7.3 MeV  
(d) 
92
U
235
 + 
0
n
1
 ? 
54
Xe
140
 + 
38
Sr
94
 + 2(
0
n
1
) + ? + 
200 MeV 
7. The stopping potential as a function of frequency 
of incident radiation is 
plotted for two 
different photoelectric 
surfaces A  and B. The 
graphs shows that the 
work function of A is 
(a) greater than that 
of B 
(b) smaller than that of B 
(c) same as that of B 
(d) such that no comparison can be done from 
given graphs 
8. The minimum wavelength of X-rays produced by 
accelerating potential V is ?. What will be the 
minimum wavelength, when the accelerating 
potential is 2 V. 
(a) 2 ? (b) 2 ? 
(c) ? 2 (d) ?/2 
9. The relation between  half life T
1/2
 of a radioactive 
sample and its mean life ? is 
(a) T
1/2
 = 0.693 t (b) t = 0.693 T
1/2
 
(c) t = T
1/2 
(d) t = 2.718 T
1/2 
10. According to Bohr’s theory the radius of electron 
in an orbit described by principal quantum 
number n and atomic number Z is proportional to 
(a) Z
2
n
2 
(b) Z
2
/n
2
 
(c) (Z
2
/n) (d) (n
2
/Z). 
11. A transistor is preferable to triode valve because it   
(a) can withstand larger changes in temperature  
(b) has higher input impedance  
(c) can handle larger powers   
(d) does not require a heater  
12. What is the value of A . A in Boolean algebra : 
(a) 0 (b) 1  
(c) A (d) A 
13. When NPN transistor is used as an amplifier then   
(a) electrons move from base to collector   
(b) holes move from emitter to base   
(c) electrons move from collector to base  
(d) holes move from base to emitter  
14. In p -type semiconductor :  
(a) major current carriers are electrons   
(b) major current carriers are mobile negative 
ions   
(c) major current carriers are mobile holes   
(d) the number of mobile holes exceeds the 
number of acceptors  
15. The diffusion current in a P -N junction is :  
(a) from n -side to p -side   
(b) from p -side & n -side   
(c) from n -side to p -side, if forward biased  
(d) from p -side to n -side, if reverse biased  
16. n -type germanium is obtained on doping intrinsic 
germanium with :  
                                   [2] 
 
 
 
(a) Phosphorus  (b) Aluminium  
(c) Boron  (d) Gold 
17. The band gap in germanium and silicon in eV 
respectively is :  
(a) 0.7, 1.1 (b) 1.1, 0.7  
(c) 1.0,0 (d) 0, 1.1  
18. An electron and a proton are injected into a 
uniform magnetic field perpendicular to it with 
the same momentum. What is the nature of their 
trajectories ? 
(a) Radius of curvature is less for electron  
(b)  Radius of curvature is more for electron 
(c) Radius of curvature is same for both  
(d) Both move along straight lines. 
19. The p–n junction diode works as insulator, if 
connected  
(a) to A.C.  (b) in forward bias  
(c) in reverse bias  (d) none of these  
20. the reverse process of pair production is called  
(a) annihilation of matter  
(b) a–decay 
(c) radioactivity 
(d) carbon–nitrogen cycle  
21. The least doped region in a transistor is  
(a) emitter  
(b) collector  
(c) base  
(d) either emitter or collector  
22. Radiowave frequency 30 MHz to 300 MHz belong 
to which of the following ? 
(a) HF (b)  UHF 
(c) VHF (d) SHF. 
23. In which of the following cases the band width as 
well as modutation increases ? 
(a) DSB (b)  SSB 
(c) AM (d) FM. 
24. What is the range of frequency of microwaves :  
(a) 3 × 10
12
 to 3 × 10
9 
Hz  
(b) 3 × 10
11
 to 1 × 10
9
 Hz 
(c) 3 × 10
10
 to 3 × 10
9 
Hz  
(d) 3 × 10
9
 to 1 × 10
9 
Hz 
25. Which of the following is not the mode of 
transmission of radiowaves from one place to 
another   
(a) Ground wave  (b) Space wave   
(c) Sky wave  (d) Carrier wave  
In every question a statement of ASSERTION is 
followed by a statement of REASON. Mark the 
correct answer out of the following choices: 
(a) If both ASSERTION and REASON are true 
and reason is the correct explanation of the 
assertion. 
(b) If both ASSERTION and REASON are true 
but reason is not the correct explanation of the 
assertion. 
(c) If ASSERTION is true but REASON is false. 
(d) If ASSERTION is false but REASON is true. 
26. Assertion: If electrons were not orbiting the 
nucleus and were stationary, they would collapse 
into the nucleus. 
Reason: There is electrostatic attraction between 
protons in the nucleus and the orbiting electrons. 
27. Assertion: A spectral line is emitted when an 
electron rotates in a fixed elliptical orbit. 
Reason: The concept of elliptical orbits was put 
forth by Sommerfeld. 
28. Assertion : Thermionic emission from the surface 
of a metal when it is heated to incandescence was 
discovered by Thomas Edison.  
Reason     : Thermions have negative charge. 
29. Assertion : A diode can be used as a rectifier.   
Reason     : Electrons are emitted by the cathode 
and collected by the anode.  
30. Assertion : In a semiconductor, the conduction 
electrons have a higher mobility than holes.   
Reason     : The electrons experience fewer 
collisions.   
Test-10 (Dual Nature of matter, Atom-molecular nuclei, Semi-conductors & 
Communication) 
 
1 C 6 B 11 
D 
16 
A 
21 
C 
26 
B 
2 C 7 B 12 A 17 A 22 C 27 D 
3 B 8 D 13 A 18 C 23 D 28 B 
4 B 9 A 14 
C 
19 
C 
24 
B 
29 
A 
5 C 10 D 15 
B 
20 A 25 D 30 C 
 
Page 3


                                   [1] 
 
 
 
(Dual Nature of matter, Atom-molecular nuclei, Semi-conductors & 
Communication)  
1. An electron and a proton are injected into a 
uniform electric field at right angle to the field 
with the same kinetic energy. What is the nature 
of their trajectories? 
(a) Electron trajectory is more curved than the 
proton trajectory  
(b)  Electron trajectory is less curved than the 
proton trajectory 
(c) Both trajectories are equally curved  
(d) Both trajectories are straight lines. 
2. When a beam of accelerated electrons hits a target, 
continuous X- ray spectrum is emitted from the 
target. Which one of the following wavelength is 
absent  in the X-rays tube is operated at 40,000 V?  
(a) 1.5Å (b)  0.5 Å 
(c) 0.25 Å (d) 1.0 Å 
3. Ultraviolet radiation of 6.2 eV falls on an 
aluminium surface (work function 4.2 eV). The 
kinetic energy in joule of the fastest electron 
emitted is approximately 
(a) 3 × 10
-
21  
(b)  3 × 10
-
19
 
(c) 3 × 10
-
17 
(d) 3 × 10
-
15
 
4. T is the half life period and T
a
 is the average life 
of a radioactive substance. Which of the following 
statement is correct ? 
(a) T > T
a
  
(b)  T is about 69% of T
a 
(c) T is inversely proportional to T
a
  
(d) T and T
a
 both are directly proportional to 
radioactive decay constant. 
5. Bi has a half life of 5 days. What time is taken by 
(7/8)th part of the sample to decay ?  
(a) 3.4 days (b)  10 days 
(c) 15 days (d) 20 days. 
6. From the following equations pick out the 
possible nuclear fusion reaction 
(a) 6
C
13
 + 
1
H
1
 ? 
6
C
14
 + 4.3 MeV  
(b) 
6
C
12
 + 
1
H
1
 ? 
7
N
13
 + 2 MeV  
(c) 
7
N
14
 + 
1
H
1
 ? 
8
O
16
 + 7.3 MeV  
(d) 
92
U
235
 + 
0
n
1
 ? 
54
Xe
140
 + 
38
Sr
94
 + 2(
0
n
1
) + ? + 
200 MeV 
7. The stopping potential as a function of frequency 
of incident radiation is 
plotted for two 
different photoelectric 
surfaces A  and B. The 
graphs shows that the 
work function of A is 
(a) greater than that 
of B 
(b) smaller than that of B 
(c) same as that of B 
(d) such that no comparison can be done from 
given graphs 
8. The minimum wavelength of X-rays produced by 
accelerating potential V is ?. What will be the 
minimum wavelength, when the accelerating 
potential is 2 V. 
(a) 2 ? (b) 2 ? 
(c) ? 2 (d) ?/2 
9. The relation between  half life T
1/2
 of a radioactive 
sample and its mean life ? is 
(a) T
1/2
 = 0.693 t (b) t = 0.693 T
1/2
 
(c) t = T
1/2 
(d) t = 2.718 T
1/2 
10. According to Bohr’s theory the radius of electron 
in an orbit described by principal quantum 
number n and atomic number Z is proportional to 
(a) Z
2
n
2 
(b) Z
2
/n
2
 
(c) (Z
2
/n) (d) (n
2
/Z). 
11. A transistor is preferable to triode valve because it   
(a) can withstand larger changes in temperature  
(b) has higher input impedance  
(c) can handle larger powers   
(d) does not require a heater  
12. What is the value of A . A in Boolean algebra : 
(a) 0 (b) 1  
(c) A (d) A 
13. When NPN transistor is used as an amplifier then   
(a) electrons move from base to collector   
(b) holes move from emitter to base   
(c) electrons move from collector to base  
(d) holes move from base to emitter  
14. In p -type semiconductor :  
(a) major current carriers are electrons   
(b) major current carriers are mobile negative 
ions   
(c) major current carriers are mobile holes   
(d) the number of mobile holes exceeds the 
number of acceptors  
15. The diffusion current in a P -N junction is :  
(a) from n -side to p -side   
(b) from p -side & n -side   
(c) from n -side to p -side, if forward biased  
(d) from p -side to n -side, if reverse biased  
16. n -type germanium is obtained on doping intrinsic 
germanium with :  
                                   [2] 
 
 
 
(a) Phosphorus  (b) Aluminium  
(c) Boron  (d) Gold 
17. The band gap in germanium and silicon in eV 
respectively is :  
(a) 0.7, 1.1 (b) 1.1, 0.7  
(c) 1.0,0 (d) 0, 1.1  
18. An electron and a proton are injected into a 
uniform magnetic field perpendicular to it with 
the same momentum. What is the nature of their 
trajectories ? 
(a) Radius of curvature is less for electron  
(b)  Radius of curvature is more for electron 
(c) Radius of curvature is same for both  
(d) Both move along straight lines. 
19. The p–n junction diode works as insulator, if 
connected  
(a) to A.C.  (b) in forward bias  
(c) in reverse bias  (d) none of these  
20. the reverse process of pair production is called  
(a) annihilation of matter  
(b) a–decay 
(c) radioactivity 
(d) carbon–nitrogen cycle  
21. The least doped region in a transistor is  
(a) emitter  
(b) collector  
(c) base  
(d) either emitter or collector  
22. Radiowave frequency 30 MHz to 300 MHz belong 
to which of the following ? 
(a) HF (b)  UHF 
(c) VHF (d) SHF. 
23. In which of the following cases the band width as 
well as modutation increases ? 
(a) DSB (b)  SSB 
(c) AM (d) FM. 
24. What is the range of frequency of microwaves :  
(a) 3 × 10
12
 to 3 × 10
9 
Hz  
(b) 3 × 10
11
 to 1 × 10
9
 Hz 
(c) 3 × 10
10
 to 3 × 10
9 
Hz  
(d) 3 × 10
9
 to 1 × 10
9 
Hz 
25. Which of the following is not the mode of 
transmission of radiowaves from one place to 
another   
(a) Ground wave  (b) Space wave   
(c) Sky wave  (d) Carrier wave  
In every question a statement of ASSERTION is 
followed by a statement of REASON. Mark the 
correct answer out of the following choices: 
(a) If both ASSERTION and REASON are true 
and reason is the correct explanation of the 
assertion. 
(b) If both ASSERTION and REASON are true 
but reason is not the correct explanation of the 
assertion. 
(c) If ASSERTION is true but REASON is false. 
(d) If ASSERTION is false but REASON is true. 
26. Assertion: If electrons were not orbiting the 
nucleus and were stationary, they would collapse 
into the nucleus. 
Reason: There is electrostatic attraction between 
protons in the nucleus and the orbiting electrons. 
27. Assertion: A spectral line is emitted when an 
electron rotates in a fixed elliptical orbit. 
Reason: The concept of elliptical orbits was put 
forth by Sommerfeld. 
28. Assertion : Thermionic emission from the surface 
of a metal when it is heated to incandescence was 
discovered by Thomas Edison.  
Reason     : Thermions have negative charge. 
29. Assertion : A diode can be used as a rectifier.   
Reason     : Electrons are emitted by the cathode 
and collected by the anode.  
30. Assertion : In a semiconductor, the conduction 
electrons have a higher mobility than holes.   
Reason     : The electrons experience fewer 
collisions.   
Test-10 (Dual Nature of matter, Atom-molecular nuclei, Semi-conductors & 
Communication) 
 
1 C 6 B 11 
D 
16 
A 
21 
C 
26 
B 
2 C 7 B 12 A 17 A 22 C 27 D 
3 B 8 D 13 A 18 C 23 D 28 B 
4 B 9 A 14 
C 
19 
C 
24 
B 
29 
A 
5 C 10 D 15 
B 
20 A 25 D 30 C 
 
                                   [3] 
 
 
 
SOLUTIONS 
 
1. The path will be parabola given by : y = 
2 2
2
x
) KE (
eE
4
1
x
mv
eE
2
1
= ; Since KE is same for both 
particles, hence both trajectories are equally 
curves.  
2. Minimum wavelength = hc/eV. 
3. E
k
 = 6.2 - 4.2 = 2eV  = 2 × 1.6 × 10
-
19
 J = 3.2 × 10
-
19
 
J 
4. T = . T / 1 and
693 . 0
a
= ?
?
; Hence T = 0.693 T
a
. 
5. A = A
0
 
n
2
1
?
?
?
?
?
?
, Here A = (1 - )
8
7
A
0
 = 
8
1
A
0
. Hence 
8
1
A
0
 = (A
0
) 
n
2
1
?
?
?
?
?
?
. This gives n = 3, Hence t = 3 × 
5 = 15 days. 
6. (b) 
7. The intersect of the graph with v -axis gives 
threshold frequency ? = hv
0
. 
8. ?
min
 = hc/eV. 
9. It is factual relation. 
10. r = ) Z / n (
me
h
2
4
2
0
p
e
 
11. Hence, efficiency is higher. 
12. A. A = 0 both when A = 0 or 1. 
13. Majority carriers in NPN transistor are electrons. 
14. (c) 
15. Positive charge carriers that is the holes diffuse 
from a region of high concentration to regions of 
lower concentration. 
16. N -Type semiconductor is obtained by doping 
with pentavalent impurities. 
17. The forbidden band for germanium (Ge) and 
silicon (Si) are 0.7 and 1.1 eV respectively. 
18. (c). 
19. (c) 
20. (a) 
21. (c) 
22. (c) 
23. (d) 
24. (b) 
25. (d) 
26. (b) Both assertion and reason are true but reason 
is not the correct explanation of the assertion. 
Both the assertion and reason are true. The 
assertion has stationary charges whereas the 
reason has moving charges, therefore, the reason 
cannot explain the assertion. 
However, there is an electrostatic force between 
the nucleus (positive charge) and the stationary 
electrons (negative charge) of the atom. This 
electrostatic force is one of attraction. If the 
electrons were not orbiting the nucleus but were 
free to move, this attractive force would draw 
them towards the nucleus. As the distance would 
go on decreasing the force of attraction would go 
on increasing and the electron would finally fall 
into the nucleus. 
(Actually this does not happen as the electrons are 
not stationary but move around the nucleus in 
definite quantized orbits.) 
27. (d) Assertion is false but reason is true. 
A spectral line will be emitted by the electron only 
when there is a change in its orbit i.e. when an 
electron goes from a higher orbit to a lower orbit. 
When the electron is in a fixed orbit it does not 
radiate energy. 
Like the model of the solar system, Sommerfield 
suggested that the orbits of the electron are not 
perfect circles. They are elliptical. This helped in 
removing some very fine discrepancies between 
the observations and predictions based on perfect 
circular orbits. 
28. (b) Both assertion and reason are true but 
reason is not the correct explanation of the 
assertion:  
The conduction -electrons/free -electrons are free 
to move within the melt. They cannot leave the 
surface due to attraction of positive ions. At 
ordinary temperatures, the average kinetic energy 
of the free electrons is insufficient to over come 
the surface barrier when a water is heat the 
average kinetic energy of free electrons also 
increases, as the temperature rise. When the 
electrons attain energy sufficient to overcome the 
surface barrier, they escape from the metal. This 
thermionic emission phenomenon was discovered 
by Thomas Alva Edison. The assertion is correct. 
Electrons emitted by heating of metals are called 
thermions. Hence, thermions carry a negative 
charge. The reason is correct. The reason does not 
explain the thermionic emission. 
29. (a) Both assertion and reason are true and 
reason is the correct explanation of the assertion. 
Electrons are emitted by the filament (cathode) 
and collected by the plate (anode). The current 
flows only in one direction from the plate to the 
cathode when the plate is at a positive potential. 
The reason is correct. This property of the diode, 
of unidirectional current is utilized in rectifying 
alternate current into a direct current. As long as 
there  is a positive potential  on the plate, the 
diode conducts but when the potential on the 
plate becomes negative the flow of current stops. 
Page 4


                                   [1] 
 
 
 
(Dual Nature of matter, Atom-molecular nuclei, Semi-conductors & 
Communication)  
1. An electron and a proton are injected into a 
uniform electric field at right angle to the field 
with the same kinetic energy. What is the nature 
of their trajectories? 
(a) Electron trajectory is more curved than the 
proton trajectory  
(b)  Electron trajectory is less curved than the 
proton trajectory 
(c) Both trajectories are equally curved  
(d) Both trajectories are straight lines. 
2. When a beam of accelerated electrons hits a target, 
continuous X- ray spectrum is emitted from the 
target. Which one of the following wavelength is 
absent  in the X-rays tube is operated at 40,000 V?  
(a) 1.5Å (b)  0.5 Å 
(c) 0.25 Å (d) 1.0 Å 
3. Ultraviolet radiation of 6.2 eV falls on an 
aluminium surface (work function 4.2 eV). The 
kinetic energy in joule of the fastest electron 
emitted is approximately 
(a) 3 × 10
-
21  
(b)  3 × 10
-
19
 
(c) 3 × 10
-
17 
(d) 3 × 10
-
15
 
4. T is the half life period and T
a
 is the average life 
of a radioactive substance. Which of the following 
statement is correct ? 
(a) T > T
a
  
(b)  T is about 69% of T
a 
(c) T is inversely proportional to T
a
  
(d) T and T
a
 both are directly proportional to 
radioactive decay constant. 
5. Bi has a half life of 5 days. What time is taken by 
(7/8)th part of the sample to decay ?  
(a) 3.4 days (b)  10 days 
(c) 15 days (d) 20 days. 
6. From the following equations pick out the 
possible nuclear fusion reaction 
(a) 6
C
13
 + 
1
H
1
 ? 
6
C
14
 + 4.3 MeV  
(b) 
6
C
12
 + 
1
H
1
 ? 
7
N
13
 + 2 MeV  
(c) 
7
N
14
 + 
1
H
1
 ? 
8
O
16
 + 7.3 MeV  
(d) 
92
U
235
 + 
0
n
1
 ? 
54
Xe
140
 + 
38
Sr
94
 + 2(
0
n
1
) + ? + 
200 MeV 
7. The stopping potential as a function of frequency 
of incident radiation is 
plotted for two 
different photoelectric 
surfaces A  and B. The 
graphs shows that the 
work function of A is 
(a) greater than that 
of B 
(b) smaller than that of B 
(c) same as that of B 
(d) such that no comparison can be done from 
given graphs 
8. The minimum wavelength of X-rays produced by 
accelerating potential V is ?. What will be the 
minimum wavelength, when the accelerating 
potential is 2 V. 
(a) 2 ? (b) 2 ? 
(c) ? 2 (d) ?/2 
9. The relation between  half life T
1/2
 of a radioactive 
sample and its mean life ? is 
(a) T
1/2
 = 0.693 t (b) t = 0.693 T
1/2
 
(c) t = T
1/2 
(d) t = 2.718 T
1/2 
10. According to Bohr’s theory the radius of electron 
in an orbit described by principal quantum 
number n and atomic number Z is proportional to 
(a) Z
2
n
2 
(b) Z
2
/n
2
 
(c) (Z
2
/n) (d) (n
2
/Z). 
11. A transistor is preferable to triode valve because it   
(a) can withstand larger changes in temperature  
(b) has higher input impedance  
(c) can handle larger powers   
(d) does not require a heater  
12. What is the value of A . A in Boolean algebra : 
(a) 0 (b) 1  
(c) A (d) A 
13. When NPN transistor is used as an amplifier then   
(a) electrons move from base to collector   
(b) holes move from emitter to base   
(c) electrons move from collector to base  
(d) holes move from base to emitter  
14. In p -type semiconductor :  
(a) major current carriers are electrons   
(b) major current carriers are mobile negative 
ions   
(c) major current carriers are mobile holes   
(d) the number of mobile holes exceeds the 
number of acceptors  
15. The diffusion current in a P -N junction is :  
(a) from n -side to p -side   
(b) from p -side & n -side   
(c) from n -side to p -side, if forward biased  
(d) from p -side to n -side, if reverse biased  
16. n -type germanium is obtained on doping intrinsic 
germanium with :  
                                   [2] 
 
 
 
(a) Phosphorus  (b) Aluminium  
(c) Boron  (d) Gold 
17. The band gap in germanium and silicon in eV 
respectively is :  
(a) 0.7, 1.1 (b) 1.1, 0.7  
(c) 1.0,0 (d) 0, 1.1  
18. An electron and a proton are injected into a 
uniform magnetic field perpendicular to it with 
the same momentum. What is the nature of their 
trajectories ? 
(a) Radius of curvature is less for electron  
(b)  Radius of curvature is more for electron 
(c) Radius of curvature is same for both  
(d) Both move along straight lines. 
19. The p–n junction diode works as insulator, if 
connected  
(a) to A.C.  (b) in forward bias  
(c) in reverse bias  (d) none of these  
20. the reverse process of pair production is called  
(a) annihilation of matter  
(b) a–decay 
(c) radioactivity 
(d) carbon–nitrogen cycle  
21. The least doped region in a transistor is  
(a) emitter  
(b) collector  
(c) base  
(d) either emitter or collector  
22. Radiowave frequency 30 MHz to 300 MHz belong 
to which of the following ? 
(a) HF (b)  UHF 
(c) VHF (d) SHF. 
23. In which of the following cases the band width as 
well as modutation increases ? 
(a) DSB (b)  SSB 
(c) AM (d) FM. 
24. What is the range of frequency of microwaves :  
(a) 3 × 10
12
 to 3 × 10
9 
Hz  
(b) 3 × 10
11
 to 1 × 10
9
 Hz 
(c) 3 × 10
10
 to 3 × 10
9 
Hz  
(d) 3 × 10
9
 to 1 × 10
9 
Hz 
25. Which of the following is not the mode of 
transmission of radiowaves from one place to 
another   
(a) Ground wave  (b) Space wave   
(c) Sky wave  (d) Carrier wave  
In every question a statement of ASSERTION is 
followed by a statement of REASON. Mark the 
correct answer out of the following choices: 
(a) If both ASSERTION and REASON are true 
and reason is the correct explanation of the 
assertion. 
(b) If both ASSERTION and REASON are true 
but reason is not the correct explanation of the 
assertion. 
(c) If ASSERTION is true but REASON is false. 
(d) If ASSERTION is false but REASON is true. 
26. Assertion: If electrons were not orbiting the 
nucleus and were stationary, they would collapse 
into the nucleus. 
Reason: There is electrostatic attraction between 
protons in the nucleus and the orbiting electrons. 
27. Assertion: A spectral line is emitted when an 
electron rotates in a fixed elliptical orbit. 
Reason: The concept of elliptical orbits was put 
forth by Sommerfeld. 
28. Assertion : Thermionic emission from the surface 
of a metal when it is heated to incandescence was 
discovered by Thomas Edison.  
Reason     : Thermions have negative charge. 
29. Assertion : A diode can be used as a rectifier.   
Reason     : Electrons are emitted by the cathode 
and collected by the anode.  
30. Assertion : In a semiconductor, the conduction 
electrons have a higher mobility than holes.   
Reason     : The electrons experience fewer 
collisions.   
Test-10 (Dual Nature of matter, Atom-molecular nuclei, Semi-conductors & 
Communication) 
 
1 C 6 B 11 
D 
16 
A 
21 
C 
26 
B 
2 C 7 B 12 A 17 A 22 C 27 D 
3 B 8 D 13 A 18 C 23 D 28 B 
4 B 9 A 14 
C 
19 
C 
24 
B 
29 
A 
5 C 10 D 15 
B 
20 A 25 D 30 C 
 
                                   [3] 
 
 
 
SOLUTIONS 
 
1. The path will be parabola given by : y = 
2 2
2
x
) KE (
eE
4
1
x
mv
eE
2
1
= ; Since KE is same for both 
particles, hence both trajectories are equally 
curves.  
2. Minimum wavelength = hc/eV. 
3. E
k
 = 6.2 - 4.2 = 2eV  = 2 × 1.6 × 10
-
19
 J = 3.2 × 10
-
19
 
J 
4. T = . T / 1 and
693 . 0
a
= ?
?
; Hence T = 0.693 T
a
. 
5. A = A
0
 
n
2
1
?
?
?
?
?
?
, Here A = (1 - )
8
7
A
0
 = 
8
1
A
0
. Hence 
8
1
A
0
 = (A
0
) 
n
2
1
?
?
?
?
?
?
. This gives n = 3, Hence t = 3 × 
5 = 15 days. 
6. (b) 
7. The intersect of the graph with v -axis gives 
threshold frequency ? = hv
0
. 
8. ?
min
 = hc/eV. 
9. It is factual relation. 
10. r = ) Z / n (
me
h
2
4
2
0
p
e
 
11. Hence, efficiency is higher. 
12. A. A = 0 both when A = 0 or 1. 
13. Majority carriers in NPN transistor are electrons. 
14. (c) 
15. Positive charge carriers that is the holes diffuse 
from a region of high concentration to regions of 
lower concentration. 
16. N -Type semiconductor is obtained by doping 
with pentavalent impurities. 
17. The forbidden band for germanium (Ge) and 
silicon (Si) are 0.7 and 1.1 eV respectively. 
18. (c). 
19. (c) 
20. (a) 
21. (c) 
22. (c) 
23. (d) 
24. (b) 
25. (d) 
26. (b) Both assertion and reason are true but reason 
is not the correct explanation of the assertion. 
Both the assertion and reason are true. The 
assertion has stationary charges whereas the 
reason has moving charges, therefore, the reason 
cannot explain the assertion. 
However, there is an electrostatic force between 
the nucleus (positive charge) and the stationary 
electrons (negative charge) of the atom. This 
electrostatic force is one of attraction. If the 
electrons were not orbiting the nucleus but were 
free to move, this attractive force would draw 
them towards the nucleus. As the distance would 
go on decreasing the force of attraction would go 
on increasing and the electron would finally fall 
into the nucleus. 
(Actually this does not happen as the electrons are 
not stationary but move around the nucleus in 
definite quantized orbits.) 
27. (d) Assertion is false but reason is true. 
A spectral line will be emitted by the electron only 
when there is a change in its orbit i.e. when an 
electron goes from a higher orbit to a lower orbit. 
When the electron is in a fixed orbit it does not 
radiate energy. 
Like the model of the solar system, Sommerfield 
suggested that the orbits of the electron are not 
perfect circles. They are elliptical. This helped in 
removing some very fine discrepancies between 
the observations and predictions based on perfect 
circular orbits. 
28. (b) Both assertion and reason are true but 
reason is not the correct explanation of the 
assertion:  
The conduction -electrons/free -electrons are free 
to move within the melt. They cannot leave the 
surface due to attraction of positive ions. At 
ordinary temperatures, the average kinetic energy 
of the free electrons is insufficient to over come 
the surface barrier when a water is heat the 
average kinetic energy of free electrons also 
increases, as the temperature rise. When the 
electrons attain energy sufficient to overcome the 
surface barrier, they escape from the metal. This 
thermionic emission phenomenon was discovered 
by Thomas Alva Edison. The assertion is correct. 
Electrons emitted by heating of metals are called 
thermions. Hence, thermions carry a negative 
charge. The reason is correct. The reason does not 
explain the thermionic emission. 
29. (a) Both assertion and reason are true and 
reason is the correct explanation of the assertion. 
Electrons are emitted by the filament (cathode) 
and collected by the plate (anode). The current 
flows only in one direction from the plate to the 
cathode when the plate is at a positive potential. 
The reason is correct. This property of the diode, 
of unidirectional current is utilized in rectifying 
alternate current into a direct current. As long as 
there  is a positive potential  on the plate, the 
diode conducts but when the potential on the 
plate becomes negative the flow of current stops. 
                                   [4] 
 
 
 
The direct current produced during the positive 
half of the cycle has the same variation as that of 
the applied alternating voltage. A single diode can 
be used as an Half -wave rectifier. A single diode 
can be used as a Half -wave rectifier. A full -wave 
rectifier, one which gives direct current in the 
complete cycle, is made using two or four diode.     
30. (c) Assertion is true but reason is false. 
Electrons do not experience fewer collisions. The 
mobility of electrons is more because they require 
less energy to move, not because they are lighter.   
Read More
Offer running on EduRev: Apply code STAYHOME200 to get INR 200 off on our premium plan EduRev Infinity!