Physics: CBSE Marking Scheme with Solution (2019-20) | Physics for Grade 12 PDF Download

 Page 1


1 
 
Class -XII 
PHYSICS 
SQP Marking Scheme 
2019-20 
 
Section – A  
1. a , ?=  (for one face) 1 
   
2. b , Conductor  1 
   
3. a , 1?. 1 
   
4. c ,12.0kJ 1 
   
5. a , speed 1 
   
6. d, virtual and inverted 1 
   
7. a, straight line 1 
   
8. d, 60
 O
 1 
   
9. b, work function 1 
   
10. b, third orbit 1 
   
11. 45
 O  
 or vertical 1 
   
12. 2 H 1 
   
13. double 1 
   
14. 1.227 A
o
 1 
   
15. 60° 1 
   
16. Difference in initial mass energy and energy associated with mass of products 
Or  
Total Kinetic energy gained in the process 
1 
   
17. Increases   1 
   
18. N o/8 1 
   
19. 0.79 eV 1 
   
20. Diodes with band gap energy in the visible spectrum range can function as LED 1 
Page 2


1 
 
Class -XII 
PHYSICS 
SQP Marking Scheme 
2019-20 
 
Section – A  
1. a , ?=  (for one face) 1 
   
2. b , Conductor  1 
   
3. a , 1?. 1 
   
4. c ,12.0kJ 1 
   
5. a , speed 1 
   
6. d, virtual and inverted 1 
   
7. a, straight line 1 
   
8. d, 60
 O
 1 
   
9. b, work function 1 
   
10. b, third orbit 1 
   
11. 45
 O  
 or vertical 1 
   
12. 2 H 1 
   
13. double 1 
   
14. 1.227 A
o
 1 
   
15. 60° 1 
   
16. Difference in initial mass energy and energy associated with mass of products 
Or  
Total Kinetic energy gained in the process 
1 
   
17. Increases   1 
   
18. N o/8 1 
   
19. 0.79 eV 1 
   
20. Diodes with band gap energy in the visible spectrum range can function as LED 1 
2 
 
 
 
OR 
Any one use 
Section – B 
 
21. When electric field E is applied on conductor force acting on free electrons 
    = -e  
                                        m = -e 
 =  
       Average thermal velocity of electron in conductor is zero 
                                      (u t) av= 0 
Average velocity of electron in conductors in t (relaxation time) = v d (drift velocity) 
     v d = (u t) av + a t 
     v d = 0 +  
 =  
 
 
 
 
 
 
1 
 
 
 
 
1 
   
22. 
 
 
 
C 2 and C 3 are in series 
   =  +  = 1 
   = 1µf  
  & C 4 are in ? 
C” = 1 + 1 = 2µf 
C” & c 5 are in series 
   =  +  ?  = 1µf 
  & c 1 are in ? 
C eq = 1 + 1 = 2µf 
Energy stored 
U =  cv
2
 =  ×2×10
-6
×6
2
 
        = 36×10
-6
J 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
1 
  
 
 
Page 3


1 
 
Class -XII 
PHYSICS 
SQP Marking Scheme 
2019-20 
 
Section – A  
1. a , ?=  (for one face) 1 
   
2. b , Conductor  1 
   
3. a , 1?. 1 
   
4. c ,12.0kJ 1 
   
5. a , speed 1 
   
6. d, virtual and inverted 1 
   
7. a, straight line 1 
   
8. d, 60
 O
 1 
   
9. b, work function 1 
   
10. b, third orbit 1 
   
11. 45
 O  
 or vertical 1 
   
12. 2 H 1 
   
13. double 1 
   
14. 1.227 A
o
 1 
   
15. 60° 1 
   
16. Difference in initial mass energy and energy associated with mass of products 
Or  
Total Kinetic energy gained in the process 
1 
   
17. Increases   1 
   
18. N o/8 1 
   
19. 0.79 eV 1 
   
20. Diodes with band gap energy in the visible spectrum range can function as LED 1 
2 
 
 
 
OR 
Any one use 
Section – B 
 
21. When electric field E is applied on conductor force acting on free electrons 
    = -e  
                                        m = -e 
 =  
       Average thermal velocity of electron in conductor is zero 
                                      (u t) av= 0 
Average velocity of electron in conductors in t (relaxation time) = v d (drift velocity) 
     v d = (u t) av + a t 
     v d = 0 +  
 =  
 
 
 
 
 
 
1 
 
 
 
 
1 
   
22. 
 
 
 
C 2 and C 3 are in series 
   =  +  = 1 
   = 1µf  
  & C 4 are in ? 
C” = 1 + 1 = 2µf 
C” & c 5 are in series 
   =  +  ?  = 1µf 
  & c 1 are in ? 
C eq = 1 + 1 = 2µf 
Energy stored 
U =  cv
2
 =  ×2×10
-6
×6
2
 
        = 36×10
-6
J 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
1 
  
 
 
3 
 
 
23. Gain in KE of particle = Qv 
 
  = K P = q pV p ----------(i)V p = V ? =V 
 = K ? = q ?V ? -----------(ii) 
 
 
(ii)/(i) 
  =   =  
  =  =  =  
 v ? : v p = 1: 
 
 
 
 
1 
 
 
 
 
1 
   
24. “The angle of incidence at which the reflected light is completely plane 
polarized, is called as Brewster’s angle (i B) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
At i = i B, reflected beam 1 to refracted beam  
? i B + r = 90 ? r = 90-i B 
Using snell’s law 
   = µ 
   = µ ?  = µ 
µ = tan  
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 
   
25. wave function 
   ? = 2.14eV 
(a) Threshold frequency  ? = h? 0 
    ? 0 =  =  
 
 
 
1 
 
Page 4


1 
 
Class -XII 
PHYSICS 
SQP Marking Scheme 
2019-20 
 
Section – A  
1. a , ?=  (for one face) 1 
   
2. b , Conductor  1 
   
3. a , 1?. 1 
   
4. c ,12.0kJ 1 
   
5. a , speed 1 
   
6. d, virtual and inverted 1 
   
7. a, straight line 1 
   
8. d, 60
 O
 1 
   
9. b, work function 1 
   
10. b, third orbit 1 
   
11. 45
 O  
 or vertical 1 
   
12. 2 H 1 
   
13. double 1 
   
14. 1.227 A
o
 1 
   
15. 60° 1 
   
16. Difference in initial mass energy and energy associated with mass of products 
Or  
Total Kinetic energy gained in the process 
1 
   
17. Increases   1 
   
18. N o/8 1 
   
19. 0.79 eV 1 
   
20. Diodes with band gap energy in the visible spectrum range can function as LED 1 
2 
 
 
 
OR 
Any one use 
Section – B 
 
21. When electric field E is applied on conductor force acting on free electrons 
    = -e  
                                        m = -e 
 =  
       Average thermal velocity of electron in conductor is zero 
                                      (u t) av= 0 
Average velocity of electron in conductors in t (relaxation time) = v d (drift velocity) 
     v d = (u t) av + a t 
     v d = 0 +  
 =  
 
 
 
 
 
 
1 
 
 
 
 
1 
   
22. 
 
 
 
C 2 and C 3 are in series 
   =  +  = 1 
   = 1µf  
  & C 4 are in ? 
C” = 1 + 1 = 2µf 
C” & c 5 are in series 
   =  +  ?  = 1µf 
  & c 1 are in ? 
C eq = 1 + 1 = 2µf 
Energy stored 
U =  cv
2
 =  ×2×10
-6
×6
2
 
        = 36×10
-6
J 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
1 
  
 
 
3 
 
 
23. Gain in KE of particle = Qv 
 
  = K P = q pV p ----------(i)V p = V ? =V 
 = K ? = q ?V ? -----------(ii) 
 
 
(ii)/(i) 
  =   =  
  =  =  =  
 v ? : v p = 1: 
 
 
 
 
1 
 
 
 
 
1 
   
24. “The angle of incidence at which the reflected light is completely plane 
polarized, is called as Brewster’s angle (i B) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
At i = i B, reflected beam 1 to refracted beam  
? i B + r = 90 ? r = 90-i B 
Using snell’s law 
   = µ 
   = µ ?  = µ 
µ = tan  
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 
   
25. wave function 
   ? = 2.14eV 
(a) Threshold frequency  ? = h? 0 
    ? 0 =  =  
 
 
 
1 
 
4 
 
                   = 5.17× H z 
(b) As k max = eV 0 = 0.6eV 
Energy of photon E = k max + ? = 0.6eV + 2.14eV 
     = 2.74eV 
Wave length of photon ? =  =  
                                                               = 4530Å 
 
 
 
 
 
 
 
1 
    
26.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
centripetal force = electrostatic attraction 
     =  
    =  --------(i) 
as = n .  
    =  put in (i)  
m . =  
     =  
 
OR 
 
Energy of electron in n = 2 is -3.4eV 
? energy in ground state = -13.6eV 
kE = -TE = +13.6eV 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
 
 
1 
 
 
E n =  ? -3.4eV =  ?                                                      
energy in ground state x = - 13.6eV. 
Page 5


1 
 
Class -XII 
PHYSICS 
SQP Marking Scheme 
2019-20 
 
Section – A  
1. a , ?=  (for one face) 1 
   
2. b , Conductor  1 
   
3. a , 1?. 1 
   
4. c ,12.0kJ 1 
   
5. a , speed 1 
   
6. d, virtual and inverted 1 
   
7. a, straight line 1 
   
8. d, 60
 O
 1 
   
9. b, work function 1 
   
10. b, third orbit 1 
   
11. 45
 O  
 or vertical 1 
   
12. 2 H 1 
   
13. double 1 
   
14. 1.227 A
o
 1 
   
15. 60° 1 
   
16. Difference in initial mass energy and energy associated with mass of products 
Or  
Total Kinetic energy gained in the process 
1 
   
17. Increases   1 
   
18. N o/8 1 
   
19. 0.79 eV 1 
   
20. Diodes with band gap energy in the visible spectrum range can function as LED 1 
2 
 
 
 
OR 
Any one use 
Section – B 
 
21. When electric field E is applied on conductor force acting on free electrons 
    = -e  
                                        m = -e 
 =  
       Average thermal velocity of electron in conductor is zero 
                                      (u t) av= 0 
Average velocity of electron in conductors in t (relaxation time) = v d (drift velocity) 
     v d = (u t) av + a t 
     v d = 0 +  
 =  
 
 
 
 
 
 
1 
 
 
 
 
1 
   
22. 
 
 
 
C 2 and C 3 are in series 
   =  +  = 1 
   = 1µf  
  & C 4 are in ? 
C” = 1 + 1 = 2µf 
C” & c 5 are in series 
   =  +  ?  = 1µf 
  & c 1 are in ? 
C eq = 1 + 1 = 2µf 
Energy stored 
U =  cv
2
 =  ×2×10
-6
×6
2
 
        = 36×10
-6
J 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
1 
  
 
 
3 
 
 
23. Gain in KE of particle = Qv 
 
  = K P = q pV p ----------(i)V p = V ? =V 
 = K ? = q ?V ? -----------(ii) 
 
 
(ii)/(i) 
  =   =  
  =  =  =  
 v ? : v p = 1: 
 
 
 
 
1 
 
 
 
 
1 
   
24. “The angle of incidence at which the reflected light is completely plane 
polarized, is called as Brewster’s angle (i B) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
At i = i B, reflected beam 1 to refracted beam  
? i B + r = 90 ? r = 90-i B 
Using snell’s law 
   = µ 
   = µ ?  = µ 
µ = tan  
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 
   
25. wave function 
   ? = 2.14eV 
(a) Threshold frequency  ? = h? 0 
    ? 0 =  =  
 
 
 
1 
 
4 
 
                   = 5.17× H z 
(b) As k max = eV 0 = 0.6eV 
Energy of photon E = k max + ? = 0.6eV + 2.14eV 
     = 2.74eV 
Wave length of photon ? =  =  
                                                               = 4530Å 
 
 
 
 
 
 
 
1 
    
26.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
centripetal force = electrostatic attraction 
     =  
    =  --------(i) 
as = n .  
    =  put in (i)  
m . =  
     =  
 
OR 
 
Energy of electron in n = 2 is -3.4eV 
? energy in ground state = -13.6eV 
kE = -TE = +13.6eV 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
 
 
1 
 
 
E n =  ? -3.4eV =  ?                                                      
energy in ground state x = - 13.6eV. 
5 
 
PE = 2TE = -2×13.6eV = -27.2eV 
 
1 
   
27.  
 
 
P-type semiconductor n-type semiconductor 
1. Density of holes >> density of 
electron 
 
2. Formed by doping trivalent 
impurity 
1. density of 
electron>>density of holes 
 
2.   formed by doping pentavalent 
       impurity 
Energy band diagram for p-type 
 
Energy band diagram of n-type 
semiconductor 
 
 
OR 
 
Energy of photon E =  = eV =2.06eV 
As E<E g (2.8eV), so photodiode cannot detect this photon.  
    
Any 
2x1
=1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 
 
1 
Section – C 
 
28.  
Principle of potentiometer, when a constant current flows through a wire of uniform 
area of cross-section, the potential drop across any length of the wire is directly 
proportional to the length. 
 Let resistance of wire AB be R 1 and its length be ‘l’ then current drawn from 
driving cell –  
I =  and hence  
P.D. across the wire AB will be  
V AB = IR 1 =  ×  
Where ‘a’ is area of cross-section of wire AB  
? =  = constant = k 
 Where R increases, current and potential difference across wire AB will be 
 
 
 
 
 
 
1 
 
 
 
 
1 
 
 
1