Science Past Year Paper SA-2 Solution(Set -2) - 2015, Class 10, CBSE - Notes | Study Past Year Papers for Class 10 - Class 10

 Page 1


Delhi – 31/1/2 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Delhi) 31/1/2 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Page 2


Delhi – 31/1/2 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Delhi) 31/1/2 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Delhi – 31/1/2 Page 2 
 
MARKING SCHEME 
CLASS X – DELHI 
Code No. 31/1/2 
 
 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. ? Name : Ethane ½  
 ? Formula : C
2
H
6
 ½ 1 
    
Q2. 1; size of image = size of object ½, ½ 1 
    
Q3. Power of a lens – the degree of convergence or divergence of light rays 
achieved by a lens/ Reciprocal of focal length of a lens 1 1 
    
Q4. Binary fission 
 
(i) Parent nucleus divides into two and 
moves to two daughter cells. 
 
(ii) No protective covering is formed. 
Multiple fission 
 
(i) Parent nucleus divides into many 
daughter nuclei, each surrounded by 
cytoplasm. 
(ii) A protective cyst is formed. 
                                 Or any other 1,1 2 
    
Q5. a) These are not unlimited and with a tremendous increase in human 
population, the demand for resources is increasing at an exponential rate. 
b) Long term perspective required to meet the needs of the present as well 
as for the generations to come. 
 
1 
 
 
1 
 
 
 
 
2 
    
Q6. Four measures:  
(i) Reforestation of the deforested areas as soon as possible. 
(ii) Ban on the indiscriminate cutting of trees. 
(iii) Felling of trees for fuel wood should be avoided. 
(iv) Overgrazing in forests should be discouraged. 
 
 
 
½ x 4 
 
 
 
2 
    
Q7. i) Na / Sodium. ½   
  Reason – The atomic size decreases from left to right due to the 
increase in the nuclear charge. 1 
 
 ii) Al / Aluminium. ½   
  Reason – The tendency to lose electrons decreases from left to right. 1  3  
    
Q8. (i) K / Potassium. 1  
 (ii) Be and Ca. 1  
 ? KX or KCl ½   
 ? Ionic / Electrovalent. ½  3  
    
    
Q9. ? Isomers are compounds having the same molecular formula but 
different structures. 1 
 
Page 3


Delhi – 31/1/2 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Delhi) 31/1/2 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Delhi – 31/1/2 Page 2 
 
MARKING SCHEME 
CLASS X – DELHI 
Code No. 31/1/2 
 
 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. ? Name : Ethane ½  
 ? Formula : C
2
H
6
 ½ 1 
    
Q2. 1; size of image = size of object ½, ½ 1 
    
Q3. Power of a lens – the degree of convergence or divergence of light rays 
achieved by a lens/ Reciprocal of focal length of a lens 1 1 
    
Q4. Binary fission 
 
(i) Parent nucleus divides into two and 
moves to two daughter cells. 
 
(ii) No protective covering is formed. 
Multiple fission 
 
(i) Parent nucleus divides into many 
daughter nuclei, each surrounded by 
cytoplasm. 
(ii) A protective cyst is formed. 
                                 Or any other 1,1 2 
    
Q5. a) These are not unlimited and with a tremendous increase in human 
population, the demand for resources is increasing at an exponential rate. 
b) Long term perspective required to meet the needs of the present as well 
as for the generations to come. 
 
1 
 
 
1 
 
 
 
 
2 
    
Q6. Four measures:  
(i) Reforestation of the deforested areas as soon as possible. 
(ii) Ban on the indiscriminate cutting of trees. 
(iii) Felling of trees for fuel wood should be avoided. 
(iv) Overgrazing in forests should be discouraged. 
 
 
 
½ x 4 
 
 
 
2 
    
Q7. i) Na / Sodium. ½   
  Reason – The atomic size decreases from left to right due to the 
increase in the nuclear charge. 1 
 
 ii) Al / Aluminium. ½   
  Reason – The tendency to lose electrons decreases from left to right. 1  3  
    
Q8. (i) K / Potassium. 1  
 (ii) Be and Ca. 1  
 ? KX or KCl ½   
 ? Ionic / Electrovalent. ½  3  
    
    
Q9. ? Isomers are compounds having the same molecular formula but 
different structures. 1 
 
Delhi – 31/1/2 Page 3 
 
  
 
 
 
  
  
 
 
 
 
 
 ½, ½ 
 
 ? Since branching is not possible, isomers (two different structures) are 
not possible for the first three members of alkane series. 1 3 
    
Q10. ? Soaps are sodium or potassium salts of long chain carboxylic acids.  ½   
 ? Detergents are ammonium or sulphonate salts. ½   
 ? Cleansing action of soap – One part of soap molecule is ionic / hydrophilic 
and dissolves in water. The other part is non-ionic / carbon chain / 
hydrophobic part which dissolves in oil. 
1 
 
 ? Thus soap molecules arrange themselves in the form of a micelle / diagram 
of a micelle. 
½  
 ? On rinsing with water, soap is washed off, lifting the oily dirt particles with 
it. 
½ 3 
    
Q11.  ? Diseases which are transmitted from an infected person to a healthy person 
due to unsafe sex. 
? Two examples –  
Bacterial disease : Gonorrhoea and syphilis 
Viral disease : Warts and AIDS 
 
? Preventive measures: use of condoms or similar coverings 
 
½ 
 
 
½ , ½ 
½ , ½ 
 
½ 
 
 
 
 
 
 
3 
Q12. ? A process where a DNA molecule produces two similar copies of 
itself in a reproducing cell. 
? Importance – 
(i) It makes possible the transmission of characters from parents to the 
next generation. 
(ii) It causes variation in the population. 
1 
 
 
1 
 
1 
 
 
 
 
 
3 
    
Q13. 
 
  
 Drawing 2  
 Two labeling – Bud, Tentacles ½, ½  3 
Page 4


Delhi – 31/1/2 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Delhi) 31/1/2 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Delhi – 31/1/2 Page 2 
 
MARKING SCHEME 
CLASS X – DELHI 
Code No. 31/1/2 
 
 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. ? Name : Ethane ½  
 ? Formula : C
2
H
6
 ½ 1 
    
Q2. 1; size of image = size of object ½, ½ 1 
    
Q3. Power of a lens – the degree of convergence or divergence of light rays 
achieved by a lens/ Reciprocal of focal length of a lens 1 1 
    
Q4. Binary fission 
 
(i) Parent nucleus divides into two and 
moves to two daughter cells. 
 
(ii) No protective covering is formed. 
Multiple fission 
 
(i) Parent nucleus divides into many 
daughter nuclei, each surrounded by 
cytoplasm. 
(ii) A protective cyst is formed. 
                                 Or any other 1,1 2 
    
Q5. a) These are not unlimited and with a tremendous increase in human 
population, the demand for resources is increasing at an exponential rate. 
b) Long term perspective required to meet the needs of the present as well 
as for the generations to come. 
 
1 
 
 
1 
 
 
 
 
2 
    
Q6. Four measures:  
(i) Reforestation of the deforested areas as soon as possible. 
(ii) Ban on the indiscriminate cutting of trees. 
(iii) Felling of trees for fuel wood should be avoided. 
(iv) Overgrazing in forests should be discouraged. 
 
 
 
½ x 4 
 
 
 
2 
    
Q7. i) Na / Sodium. ½   
  Reason – The atomic size decreases from left to right due to the 
increase in the nuclear charge. 1 
 
 ii) Al / Aluminium. ½   
  Reason – The tendency to lose electrons decreases from left to right. 1  3  
    
Q8. (i) K / Potassium. 1  
 (ii) Be and Ca. 1  
 ? KX or KCl ½   
 ? Ionic / Electrovalent. ½  3  
    
    
Q9. ? Isomers are compounds having the same molecular formula but 
different structures. 1 
 
Delhi – 31/1/2 Page 3 
 
  
 
 
 
  
  
 
 
 
 
 
 ½, ½ 
 
 ? Since branching is not possible, isomers (two different structures) are 
not possible for the first three members of alkane series. 1 3 
    
Q10. ? Soaps are sodium or potassium salts of long chain carboxylic acids.  ½   
 ? Detergents are ammonium or sulphonate salts. ½   
 ? Cleansing action of soap – One part of soap molecule is ionic / hydrophilic 
and dissolves in water. The other part is non-ionic / carbon chain / 
hydrophobic part which dissolves in oil. 
1 
 
 ? Thus soap molecules arrange themselves in the form of a micelle / diagram 
of a micelle. 
½  
 ? On rinsing with water, soap is washed off, lifting the oily dirt particles with 
it. 
½ 3 
    
Q11.  ? Diseases which are transmitted from an infected person to a healthy person 
due to unsafe sex. 
? Two examples –  
Bacterial disease : Gonorrhoea and syphilis 
Viral disease : Warts and AIDS 
 
? Preventive measures: use of condoms or similar coverings 
 
½ 
 
 
½ , ½ 
½ , ½ 
 
½ 
 
 
 
 
 
 
3 
Q12. ? A process where a DNA molecule produces two similar copies of 
itself in a reproducing cell. 
? Importance – 
(i) It makes possible the transmission of characters from parents to the 
next generation. 
(ii) It causes variation in the population. 
1 
 
 
1 
 
1 
 
 
 
 
 
3 
    
Q13. 
 
  
 Drawing 2  
 Two labeling – Bud, Tentacles ½, ½  3 
Delhi – 31/1/2 Page 4 
 
    
Q14. Speciation : formation of new species from the pre-existing population. 
 
Four factors : 
(i) Genetic Drift 
(ii) Natural Selection 
(iii) Geographical Isolation 
(iv) Change in gene / mutation 
1 
 
 
 
 
½ x 4 
 
 
 
 
 
3 
    
Q15. (i) No, the structure of the eye in each of the organisms is different. 
(ii) ? Fossils of certain dinosaurs / reptiles show imprints of feathers 
along    
   with their bones but they could not fly presumably using the 
feathers  
   for insulation; 
? Later they developed / evolved and adapted feathers for flight, 
thus becoming the ancestors of present day birds. (OR any other 
suitable evidence/example) 
½, ½ 
1 
 
 
1 
 
 
 
 
3 
    
Q16.  (a) No, it pollutes air. 
 
Advantage:  
Segregation of wastes into biodegradable and non biodegradable wastes at 
the initial stage of disposal saves time and energy. 
 
(b) By putting wastes in proper dustbins 
                                                                                   Or any other 
½, ½ 
 
 
1 
 
 
1 
 
 
 
 
 
 
3 
    
Q17. The candidate may choose any two of the following rays:   
 i) A ray parallel to the principal axis, after reflection, will pass through 
the principal focus of a concave mirror. 
ii) A ray passing through the principal focus of a concave mirror after 
reflection will emerge parallel to the principal axis. 
iii) A ray passing through the centre of curvature of a concave mirror after 
reflection is reflected back along the same path. 
iv) A ray incident obliquely to the principal axis towards the pole of a 
concave mirror is reflected obliquely, making equal angles with the 
principal axis. 
(any two) 1 × 2  
 
 or a similar representation  1 3 
 Note: The candidate must draw the ray diagram as per the two rays chosen 
by him/her. In the diagram shown above first two rays have been 
chosen/used. 
  
    
Page 5


Delhi – 31/1/2 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Delhi) 31/1/2 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Delhi – 31/1/2 Page 2 
 
MARKING SCHEME 
CLASS X – DELHI 
Code No. 31/1/2 
 
 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. ? Name : Ethane ½  
 ? Formula : C
2
H
6
 ½ 1 
    
Q2. 1; size of image = size of object ½, ½ 1 
    
Q3. Power of a lens – the degree of convergence or divergence of light rays 
achieved by a lens/ Reciprocal of focal length of a lens 1 1 
    
Q4. Binary fission 
 
(i) Parent nucleus divides into two and 
moves to two daughter cells. 
 
(ii) No protective covering is formed. 
Multiple fission 
 
(i) Parent nucleus divides into many 
daughter nuclei, each surrounded by 
cytoplasm. 
(ii) A protective cyst is formed. 
                                 Or any other 1,1 2 
    
Q5. a) These are not unlimited and with a tremendous increase in human 
population, the demand for resources is increasing at an exponential rate. 
b) Long term perspective required to meet the needs of the present as well 
as for the generations to come. 
 
1 
 
 
1 
 
 
 
 
2 
    
Q6. Four measures:  
(i) Reforestation of the deforested areas as soon as possible. 
(ii) Ban on the indiscriminate cutting of trees. 
(iii) Felling of trees for fuel wood should be avoided. 
(iv) Overgrazing in forests should be discouraged. 
 
 
 
½ x 4 
 
 
 
2 
    
Q7. i) Na / Sodium. ½   
  Reason – The atomic size decreases from left to right due to the 
increase in the nuclear charge. 1 
 
 ii) Al / Aluminium. ½   
  Reason – The tendency to lose electrons decreases from left to right. 1  3  
    
Q8. (i) K / Potassium. 1  
 (ii) Be and Ca. 1  
 ? KX or KCl ½   
 ? Ionic / Electrovalent. ½  3  
    
    
Q9. ? Isomers are compounds having the same molecular formula but 
different structures. 1 
 
Delhi – 31/1/2 Page 3 
 
  
 
 
 
  
  
 
 
 
 
 
 ½, ½ 
 
 ? Since branching is not possible, isomers (two different structures) are 
not possible for the first three members of alkane series. 1 3 
    
Q10. ? Soaps are sodium or potassium salts of long chain carboxylic acids.  ½   
 ? Detergents are ammonium or sulphonate salts. ½   
 ? Cleansing action of soap – One part of soap molecule is ionic / hydrophilic 
and dissolves in water. The other part is non-ionic / carbon chain / 
hydrophobic part which dissolves in oil. 
1 
 
 ? Thus soap molecules arrange themselves in the form of a micelle / diagram 
of a micelle. 
½  
 ? On rinsing with water, soap is washed off, lifting the oily dirt particles with 
it. 
½ 3 
    
Q11.  ? Diseases which are transmitted from an infected person to a healthy person 
due to unsafe sex. 
? Two examples –  
Bacterial disease : Gonorrhoea and syphilis 
Viral disease : Warts and AIDS 
 
? Preventive measures: use of condoms or similar coverings 
 
½ 
 
 
½ , ½ 
½ , ½ 
 
½ 
 
 
 
 
 
 
3 
Q12. ? A process where a DNA molecule produces two similar copies of 
itself in a reproducing cell. 
? Importance – 
(i) It makes possible the transmission of characters from parents to the 
next generation. 
(ii) It causes variation in the population. 
1 
 
 
1 
 
1 
 
 
 
 
 
3 
    
Q13. 
 
  
 Drawing 2  
 Two labeling – Bud, Tentacles ½, ½  3 
Delhi – 31/1/2 Page 4 
 
    
Q14. Speciation : formation of new species from the pre-existing population. 
 
Four factors : 
(i) Genetic Drift 
(ii) Natural Selection 
(iii) Geographical Isolation 
(iv) Change in gene / mutation 
1 
 
 
 
 
½ x 4 
 
 
 
 
 
3 
    
Q15. (i) No, the structure of the eye in each of the organisms is different. 
(ii) ? Fossils of certain dinosaurs / reptiles show imprints of feathers 
along    
   with their bones but they could not fly presumably using the 
feathers  
   for insulation; 
? Later they developed / evolved and adapted feathers for flight, 
thus becoming the ancestors of present day birds. (OR any other 
suitable evidence/example) 
½, ½ 
1 
 
 
1 
 
 
 
 
3 
    
Q16.  (a) No, it pollutes air. 
 
Advantage:  
Segregation of wastes into biodegradable and non biodegradable wastes at 
the initial stage of disposal saves time and energy. 
 
(b) By putting wastes in proper dustbins 
                                                                                   Or any other 
½, ½ 
 
 
1 
 
 
1 
 
 
 
 
 
 
3 
    
Q17. The candidate may choose any two of the following rays:   
 i) A ray parallel to the principal axis, after reflection, will pass through 
the principal focus of a concave mirror. 
ii) A ray passing through the principal focus of a concave mirror after 
reflection will emerge parallel to the principal axis. 
iii) A ray passing through the centre of curvature of a concave mirror after 
reflection is reflected back along the same path. 
iv) A ray incident obliquely to the principal axis towards the pole of a 
concave mirror is reflected obliquely, making equal angles with the 
principal axis. 
(any two) 1 × 2  
 
 or a similar representation  1 3 
 Note: The candidate must draw the ray diagram as per the two rays chosen 
by him/her. In the diagram shown above first two rays have been 
chosen/used. 
  
    
Delhi – 31/1/2 Page 5 
 
Q18. 
 
1  
 ? Light from the Sun near the horizon passes through thicker layers of 
air and longer distance 1  
 ? Most of the blue light and shorter wavelengths of sunlight are 
scattered away by the particles. Light of larger wavelength reaches us 
giving the reddish appearance  1 3 
    
Q19. 
cm 3
1
? ? h cm 30 ? ? u cm 60 ? ? v   
 
u v f
1 1 1
? ? 
½ 
 
 
30
1
60
1 1
?
?
?
?
f
 
½ 
 
 
60
3
30
1
60
1 1 ?
? ? ?
f
 
  
 
? cm 20 ? ? f 
1  
 Lens – Convex lens 1  
 
cm 6 cm 3
cm 0 3
cm 60
? ? ?
?
?
? ? ? ? h
u
v
h 
2 5 
    
Q20. a) Statement of laws of Refraction of light (two laws) 1 × 2  
     
  When a ray of light travels from vacuum or air into a given medium 
then ratio of sin i to sin r is called absolute refractive index of the 
medium. ½ 
 
  
medium in the light  of Speed
vacuum in light of Speed
index refractive Absolute ?  
½ 
 
 b) 
0 . 2 ?
A
n ; 5 . 1 ?
B
n m/s 10 2
8
? ?
B
v 
 
 
  i) 
B
B
v
c
n ? 
½ 
 
   
? m/s 10 3 m/s 10 . 2 5 . 1
8 8
? ? ? ? ?
B B
v n c 
½ 
 
  ii) 
A
A
v
c
n ? 
 
 
   
? m/s 10 5 . 1
2
m/s 10 3
8
8
? ?
?
? ?
A
A
n
c
v 
1 5