CBSE Physics Past year paper (Solutions) - 2017, Class 12 Class 12 Notes | EduRev

Physics Class 12

Class 12 : CBSE Physics Past year paper (Solutions) - 2017, Class 12 Class 12 Notes | EduRev

 Page 1


  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
CBSE 
Class XII Physics – Set 1 
Board Paper – All India – 2017 Solution 
 
SECTION A 
 
1. Nichrome wire is heated more  
? ?
22
nichrome copper
nichrome copper
Heat dissipate in a wire is given by 
H I Rt I t
A
H I, and A remains same
But
HH
?
??
? ? ?
? ? ?
??
 
 
2. Yes. As an electromagnetic wave is a combination of electric and magnetic 
fields, it carries both energy and momentum. It is given by 
hC
E
p mC
?
?
?
 
where  
c = Speed of EM wave in vacuum  
? = Wavelength of EM wave 
 
3. If the incident violet light is replaced with red light, then the angle of minimum 
deviation of a glass prism decreases. 
 
4. Photoelectric effect shows the quantum nature of electromagnetic radiation. 
 
5. According to Lenz law, Plate A of the capacitor is at a higher potential than Plate 
B, i.e. polarity of Plate A will be positive with respect to Plate B. 
 
 
  
Page 2


  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
CBSE 
Class XII Physics – Set 1 
Board Paper – All India – 2017 Solution 
 
SECTION A 
 
1. Nichrome wire is heated more  
? ?
22
nichrome copper
nichrome copper
Heat dissipate in a wire is given by 
H I Rt I t
A
H I, and A remains same
But
HH
?
??
? ? ?
? ? ?
??
 
 
2. Yes. As an electromagnetic wave is a combination of electric and magnetic 
fields, it carries both energy and momentum. It is given by 
hC
E
p mC
?
?
?
 
where  
c = Speed of EM wave in vacuum  
? = Wavelength of EM wave 
 
3. If the incident violet light is replaced with red light, then the angle of minimum 
deviation of a glass prism decreases. 
 
4. Photoelectric effect shows the quantum nature of electromagnetic radiation. 
 
5. According to Lenz law, Plate A of the capacitor is at a higher potential than Plate 
B, i.e. polarity of Plate A will be positive with respect to Plate B. 
 
 
  
  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
SECTION B 
 
6.  
 
Intensity distribution graph for single slit diffraction 
 
 
Difference between interference pattern and diffraction pattern 
 
Interference Diffraction 
It is due to the superposition of two 
waves coming from two coherent 
sources. 
It is due to the superposition of 
secondary wavelets originating from 
different parts of the same wavefront. 
Width of the interference bands is 
equal. 
Width of diffraction bands is not the 
same. 
 
  
Page 3


  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
CBSE 
Class XII Physics – Set 1 
Board Paper – All India – 2017 Solution 
 
SECTION A 
 
1. Nichrome wire is heated more  
? ?
22
nichrome copper
nichrome copper
Heat dissipate in a wire is given by 
H I Rt I t
A
H I, and A remains same
But
HH
?
??
? ? ?
? ? ?
??
 
 
2. Yes. As an electromagnetic wave is a combination of electric and magnetic 
fields, it carries both energy and momentum. It is given by 
hC
E
p mC
?
?
?
 
where  
c = Speed of EM wave in vacuum  
? = Wavelength of EM wave 
 
3. If the incident violet light is replaced with red light, then the angle of minimum 
deviation of a glass prism decreases. 
 
4. Photoelectric effect shows the quantum nature of electromagnetic radiation. 
 
5. According to Lenz law, Plate A of the capacitor is at a higher potential than Plate 
B, i.e. polarity of Plate A will be positive with respect to Plate B. 
 
 
  
  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
SECTION B 
 
6.  
 
Intensity distribution graph for single slit diffraction 
 
 
Difference between interference pattern and diffraction pattern 
 
Interference Diffraction 
It is due to the superposition of two 
waves coming from two coherent 
sources. 
It is due to the superposition of 
secondary wavelets originating from 
different parts of the same wavefront. 
Width of the interference bands is 
equal. 
Width of diffraction bands is not the 
same. 
 
  
  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
OR 
 
According to law of Malus, when a beam of completely plane polarised light is 
incident on an analyser ?, resultant intensity of light (I) transmitted from the 
analyser varies directly as the square of cosine of angle between the plane of the 
analyser and polariser. 
? ?
? ?
? ?
? ?
2
2
o
o
I cos
I I cos ........ Equation 1
When 0 or 180  
cos 1
I I ........ Equation 2
When 90
c
polarizer and anal
os cos90 0
yzer and parallel
In unpolarised light,
I 0 ........ Equati 
 vib
on 3
??
? ? ?
? ? ? ? ? ?
? ? ?
??
? ? ?
??
?
??
??
?
? ?
2
av
2
0
2
2
0
rations are probable in all the
direction in a plane perpendicular to the direction of propa
 
cos
gation
cos 
1 cos2
                 
2
. 
can have any value from 0 and 2 . 
1
d
2
1
2
 
d
?
?
?
? ? ?
??
??
?? ??
??
?
?
?
?
?
?
? ?
2
0
2
o
o
o
sin2
               0
2
            
1
22
1
2
Using the law of malu
    
I I cos
s
1
2
I
I
2
I
?
?? ?
?
??
??
??
??
? ? ?
?
??
?
?
 
Graph: 
 
 
  
Page 4


  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
CBSE 
Class XII Physics – Set 1 
Board Paper – All India – 2017 Solution 
 
SECTION A 
 
1. Nichrome wire is heated more  
? ?
22
nichrome copper
nichrome copper
Heat dissipate in a wire is given by 
H I Rt I t
A
H I, and A remains same
But
HH
?
??
? ? ?
? ? ?
??
 
 
2. Yes. As an electromagnetic wave is a combination of electric and magnetic 
fields, it carries both energy and momentum. It is given by 
hC
E
p mC
?
?
?
 
where  
c = Speed of EM wave in vacuum  
? = Wavelength of EM wave 
 
3. If the incident violet light is replaced with red light, then the angle of minimum 
deviation of a glass prism decreases. 
 
4. Photoelectric effect shows the quantum nature of electromagnetic radiation. 
 
5. According to Lenz law, Plate A of the capacitor is at a higher potential than Plate 
B, i.e. polarity of Plate A will be positive with respect to Plate B. 
 
 
  
  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
SECTION B 
 
6.  
 
Intensity distribution graph for single slit diffraction 
 
 
Difference between interference pattern and diffraction pattern 
 
Interference Diffraction 
It is due to the superposition of two 
waves coming from two coherent 
sources. 
It is due to the superposition of 
secondary wavelets originating from 
different parts of the same wavefront. 
Width of the interference bands is 
equal. 
Width of diffraction bands is not the 
same. 
 
  
  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
OR 
 
According to law of Malus, when a beam of completely plane polarised light is 
incident on an analyser ?, resultant intensity of light (I) transmitted from the 
analyser varies directly as the square of cosine of angle between the plane of the 
analyser and polariser. 
? ?
? ?
? ?
? ?
2
2
o
o
I cos
I I cos ........ Equation 1
When 0 or 180  
cos 1
I I ........ Equation 2
When 90
c
polarizer and anal
os cos90 0
yzer and parallel
In unpolarised light,
I 0 ........ Equati 
 vib
on 3
??
? ? ?
? ? ? ? ? ?
? ? ?
??
? ? ?
??
?
??
??
?
? ?
2
av
2
0
2
2
0
rations are probable in all the
direction in a plane perpendicular to the direction of propa
 
cos
gation
cos 
1 cos2
                 
2
. 
can have any value from 0 and 2 . 
1
d
2
1
2
 
d
?
?
?
? ? ?
??
??
?? ??
??
?
?
?
?
?
?
? ?
2
0
2
o
o
o
sin2
               0
2
            
1
22
1
2
Using the law of malu
    
I I cos
s
1
2
I
I
2
I
?
?? ?
?
??
??
??
??
? ? ?
?
??
?
?
 
Graph: 
 
 
  
  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
7.  
(a) X-rays: Used as a diagnostic tool in medicine and as a treatment for certain 
forms of cancer. 
(b) Microwaves: Used in radar systems in aircraft navigation. 
 
8. Consider a charge q moving with velocity v in the presence of electric and 
magnetic fields. The force on an electric charge q due to both of them is 
? ? ? ?
? ?
? ?
? ?
electric magnetic
where
v velocity of the charge
r location of the charge at a given time
F q E r v B r
F F F ........ Equation 1
=
 t
E r Electric field  
B r Magnetic field
?? ? ? ?
??
? ? ?
?
?
?
 
Let us consider a simple case in which electric and magnetic fields are 
perpendicular to each other and also perpendicular to the velocity of the 
particle. 
 
 
 
? ?
E
B
F qE
qEj.F
q v B
ˆ
q vi Bk
qBj
?
?
??
??
??
 
? ?
F q E vB j ? ? ? 
Thus, electric and magnetic forces are in opposite directions.  
Suppose we adjust the values of E and B such that magnitudes of the two forces 
are equal, then the total force on the charge is zero and the charge will move in 
the fields undeflected. This happens when  
Page 5


  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
CBSE 
Class XII Physics – Set 1 
Board Paper – All India – 2017 Solution 
 
SECTION A 
 
1. Nichrome wire is heated more  
? ?
22
nichrome copper
nichrome copper
Heat dissipate in a wire is given by 
H I Rt I t
A
H I, and A remains same
But
HH
?
??
? ? ?
? ? ?
??
 
 
2. Yes. As an electromagnetic wave is a combination of electric and magnetic 
fields, it carries both energy and momentum. It is given by 
hC
E
p mC
?
?
?
 
where  
c = Speed of EM wave in vacuum  
? = Wavelength of EM wave 
 
3. If the incident violet light is replaced with red light, then the angle of minimum 
deviation of a glass prism decreases. 
 
4. Photoelectric effect shows the quantum nature of electromagnetic radiation. 
 
5. According to Lenz law, Plate A of the capacitor is at a higher potential than Plate 
B, i.e. polarity of Plate A will be positive with respect to Plate B. 
 
 
  
  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
SECTION B 
 
6.  
 
Intensity distribution graph for single slit diffraction 
 
 
Difference between interference pattern and diffraction pattern 
 
Interference Diffraction 
It is due to the superposition of two 
waves coming from two coherent 
sources. 
It is due to the superposition of 
secondary wavelets originating from 
different parts of the same wavefront. 
Width of the interference bands is 
equal. 
Width of diffraction bands is not the 
same. 
 
  
  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
OR 
 
According to law of Malus, when a beam of completely plane polarised light is 
incident on an analyser ?, resultant intensity of light (I) transmitted from the 
analyser varies directly as the square of cosine of angle between the plane of the 
analyser and polariser. 
? ?
? ?
? ?
? ?
2
2
o
o
I cos
I I cos ........ Equation 1
When 0 or 180  
cos 1
I I ........ Equation 2
When 90
c
polarizer and anal
os cos90 0
yzer and parallel
In unpolarised light,
I 0 ........ Equati 
 vib
on 3
??
? ? ?
? ? ? ? ? ?
? ? ?
??
? ? ?
??
?
??
??
?
? ?
2
av
2
0
2
2
0
rations are probable in all the
direction in a plane perpendicular to the direction of propa
 
cos
gation
cos 
1 cos2
                 
2
. 
can have any value from 0 and 2 . 
1
d
2
1
2
 
d
?
?
?
? ? ?
??
??
?? ??
??
?
?
?
?
?
?
? ?
2
0
2
o
o
o
sin2
               0
2
            
1
22
1
2
Using the law of malu
    
I I cos
s
1
2
I
I
2
I
?
?? ?
?
??
??
??
??
? ? ?
?
??
?
?
 
Graph: 
 
 
  
  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
7.  
(a) X-rays: Used as a diagnostic tool in medicine and as a treatment for certain 
forms of cancer. 
(b) Microwaves: Used in radar systems in aircraft navigation. 
 
8. Consider a charge q moving with velocity v in the presence of electric and 
magnetic fields. The force on an electric charge q due to both of them is 
? ? ? ?
? ?
? ?
? ?
electric magnetic
where
v velocity of the charge
r location of the charge at a given time
F q E r v B r
F F F ........ Equation 1
=
 t
E r Electric field  
B r Magnetic field
?? ? ? ?
??
? ? ?
?
?
?
 
Let us consider a simple case in which electric and magnetic fields are 
perpendicular to each other and also perpendicular to the velocity of the 
particle. 
 
 
 
? ?
E
B
F qE
qEj.F
q v B
ˆ
q vi Bk
qBj
?
?
??
??
??
 
? ?
F q E vB j ? ? ? 
Thus, electric and magnetic forces are in opposite directions.  
Suppose we adjust the values of E and B such that magnitudes of the two forces 
are equal, then the total force on the charge is zero and the charge will move in 
the fields undeflected. This happens when  
  
 
CBSE XII  | PHYSICS 
Board Paper – All India – Set 1 – Solution 2017 
 
     
qE = qvB 
or 
E
or v
B
? 
This condition can be used to select charged particles of a particular velocity out 
of a beam containing charges moving with different speeds (irrespective of their 
charge and mass). The crossed E and B fields therefore serve as a velocity 
selector. 
 
9. It is given that the energy of the electron beam used to bombard gaseous 
hydrogen at room temperature is 12.5 eV.  
Also, the energy of the gaseous hydrogen in its ground state at room 
temperature is -13.6 eV. 
When gaseous hydrogen is bombarded with an electron beam, the energy of the 
gaseous hydrogen becomes -13.6 + 12.5 eV = -1.1 eV. 
Orbital energy related to orbit level (n) is  
? ?
? ?
2
2
13.6
E eV
n
For n 3,
13.6 13.6
E eV eV 1.5 eV 
9
3
?
?
?
??
? ? ? ? ?
 
This energy is approximately equal to the energy of gaseous hydrogen.  
This implies that the electron has jumped from n = 1 to n = 3 level.  
During its de-excitation, electrons can jump from n = 3 to n = 1 directly, which 
forms a line of the Lyman series of the hydrogen spectrum.  
Relation for wave number for the Lyman series is 
? ?
? ?
22
22
1
7
1
7
1
7
7
1
1
1 1 1
R
1n
For first member n 3
1 1 1 1 1
RR
19 1
3
1 9 1
1.097 10 ......... 
9
where Rydberg constant R 1.
18
1.097 10
9
1.025 10
097 10
m
m
?
?
??
??
??
??
?
??
?
??
??
??
? ? ? ? ?
??
? ??
??
??
? ??
? ? ?
??
?
??
? ? ? ?
?
? ? ? ?
 
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