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CBSE Class 10 Science Solved Practice Paper SA-II: Set-I

Nov 3, 2015 17:31 IST

    Find CBSE Class 10 Science Solved Practice Paper for the Summative Assessment – II. These questions will not only help the students to prepare for exams in a better manner, but will also help them in understanding the depth with which a topic should be studied.

    Few sample questions from the Question Paper are given below:

    Q. What are Isomers? State two properties of carbon which lead to the huge number of carbon compound.

    Ans. Isomers are those compounds which have same molecular formula but different structures.

    For example: Pentane, C5H12, has three chain isomers as follows:

    Q. How many 'X' chromosomes are present in body cells of humans in a:  

    (i) Male

    (ii) Female? 

    Describe the role of sex chromosomes in deciding the sex of the child.

    Ans.

    (i) A Male`s body cell contains only one X chromosome and the other one is a Y chromosome. 50 % of the male gametes (sperms) carry X-chromosome and the rest 50 % carry Y-chromosome. 

    (ii) A Female`s body cell contains two X- chromosomes. Female gametes (ova) contain similar type of chromosomes i.e. all carry one X- chromosome. 

    (iii) Sex chromosomes play a vital role in deciding the sex of the child. Males contain XY chromosomes while females contain XX chromosomes. When an egg is fertilized by a sperm carrying X- chromosome, the zygote thus developed is a female (XX condition). When an egg is fertilized by a sperm carrying Y- chromosome, the zygote thus developed is a male (XY condition).

    Q. Justify the statement giving examples: ‘‘It is possible that a trait is inherited but may not be expressed.’’

    Ans. Yes, it is possible that a trait is inherited but may not be expressed. 

    For Example: When tall garden pea plants are crossed with short pea plants, only tall pea plants are obtained in F1 generation.   

    Further after self pollination of  tall F1 plants, both  tall  and  dwarf  plants  are  obtained  in  F2 generation in the ratio 3:1.    

    Reoccurrence of this character, a  passive  trait  in  F2  generation  shows that  this trait of short height  was  present  in  individuals  of  F1  but  it was not expressed (due to the presence of tallness, a dominant trait.)

    Q. Write the importance of ciliary muscles in the human eye.  Name the defect of  vision  that  arises  due  to  gradual  weakening  of  the  ciliary muscles  in  old  age. What type of lenses are required by the persons suffering from this defect to see the objects clearly?

    Ans. Ciliary muscles play a vital role in altering the curvature of the eye lenses thereby  adjusting the focal length of the eye lenses to enable focusing objects at varying distances.

    The defect of  vision  that  arises  due  to  gradual  weakening  of  the  ciliary muscles  in    old  age is called Presbyopia.

    Bifocal lenses are required by the persons suffering from this defect to see the objects clearly.

    Q. An object of height 5 cm is placed perpendicular to the principal axis of a concave lens of  focal  length  10  cm.  If  the  distance  of  the  object  from  the optical centre of the lens is 20 cm, determine the position, nature and size of the image formed  using the lens formula.

    Ans.


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