Board Paper of Class 10 2017 Science (SET 3) - Solutions

• Question 1
  Write the molecular formula of the first two members of the homologous series having functional group .
    VIEW SOLUTION

• Question 2
  What is fertilisation? Where does it occur in a human female?   VIEW SOLUTION

• Question 3
  List any two abiotic components of an ecosystem.  VIEW SOLUTION

• Question 4
  Redraw the following diagram on your answer-sheet and show the path of the reflected ray. Also mark the angle of incidence (∠i) and the angle of reflection (∠r) on the diagram.
  
  VIEW SOLUTION

• Question 5
  Suggest any two ways by which the balance between the environment and industrial development is maintained so as to help undisturbed survival of the organisms on the Earth.  VIEW SOLUTION

• Question 6
  Where and how did "Chipko Andolan" start in our country? How did this movement ultimately benefit the local people?  VIEW SOLUTION

• Question 7
  Explain, giving reason, why carbon neither forms C⁴⁺ cations nor C⁴⁻ anions, but forms covalent compounds which are bad conductors of electricity and have low melting point and low boiling point.    VIEW SOLUTION

• Question 8
  What are hydrocarbons? Write the general formula of (i) saturated hydrocarbons, and (ii) unsaturated hydrocarbons and draw the structure of one hydrocarbon of each type.   VIEW SOLUTION

• Question 9
  Why is atomic number considered to be a more appropriate parameter than atomic mass for the classification of elements in a periodic table? How does the metallic character of elements vary as we move (i) from left to right in a period, and (ii) top to bottom in a group in the modern periodic table? Give reasons to justify your answers.  VIEW SOLUTION

• Question 10
  The atomic number of an element is 12.  (3)
  
  (a) Write its electronic configuration and determine its valency.
  
  (b) Is it more reactive or less reactive than Ca (atomic number 20)? Justify your answer giving reason.
  
  (c) Is it a metal or a non-metal?
  
  (d) Write the formula of its oxide. VIEW SOLUTION

• Question 11
  Name the two types of mammalian gametes. How are these different from each other? Name the type of reproduction they are involved in. Write the advantage of this type of reproduction.  VIEW SOLUTION

• Question 12
  How do variations arise in organisms? "Variation is useful for the survival of species." Justify this statement with the help of an example.  (3) VIEW SOLUTION

• Question 13
  What is contraception? Name any two methods. How does the use of these methods have a direct effect on the health and prosperity of a family? State any three points.   VIEW SOLUTION

• Question 14
  List any three factors and mention how they could lead to the rise of a new species.  VIEW SOLUTION

• Question 15
  What are fossils? How do they act as an evidence for organic evolution?  VIEW SOLUTION

• Question 16
  The magnification of an image formed by a lens is −1. If the distance between the object and its image is 60 cm, what is the distance of the object from the optical centre of the lens? Find the nature and focal length of the lens. If the object is displaced 20 cm towards the optical centre of the lens, where would the image be formed and what would be its nature? Draw a ray diagram to justify your answer.   VIEW SOLUTION

• Question 17
  Using the phenomenon of scattering of light, explain why there is a difference in the colour of the sun as it appears during sunrise and at noon.   (3) VIEW SOLUTION

• Question 18
  Your mother always thought that fruit juices are very healthy for everyone. One day she read in the newspaper that some brands of fruit juices in the market have been found to contain certain level of pesticides in them. She got worried as pesticides are injurious to our health.
  (a) How would you explain to your mother about fruit juices getting contaminated with pesticides?
  (b) It is said that when these harmful pesticides enter our body as well as in the bodies of other organisms they get accumulated and beyond a limit cause harm and damage to our organs. Name the phenomenon and write about it.  VIEW SOLUTION

• Question 19
  What are fossils? How are fossils formed and how is their age determined? State the importance of fossils in the study of evolution.  VIEW SOLUTION

• Question 20
  Give one example each of unisexual and bisexual flowers. Differentiate between the two types of pollination that occur in flowers. What happens when a pollen lands on a suitable stigma? Write about the events that occur till the seed formation in the ovary.  VIEW SOLUTION

• Question 21
  What are esters? How are esters prepared? Write the chemical equation for the reaction involved. What happens when an ester reacts with sodium hydroxide? Write the chemical equation for the reaction and also state the name and use of this reaction.    VIEW SOLUTION

• Question 22
  (a) Write the functions of each of the following parts of the human eye:
  (i) Cornea
  (ii) Iris
  (iii) Crystalline (Eye) lens
  (iv) Ciliary muscles
  (v) Retina
  
  (b) A person is unable to see distinctly the objects closer than 1 m. Name the defect of vision he is suffering from. Draw ray diagrams to illustrate the cause of the defect and its correction by suitable lens.  VIEW SOLUTION

• Question 23
  Analyse the following observation table showing variation of image-distance (v) with object-distance (u) in case of a convex lens and answer the questions that follow without doing any calculations:
   

  S. No.	Object-Distance u (cm)	Image-Distance v (cm)
  1	–60	+12
  2	–30	+15
  3	–20	+20
  4	–15	+30
  5	–12	+60
  6	–9	+90

  
  (a) What is the focal length of the convex lens? State reason for your answer.
  (b) For what object-distance (u) is the corresponding image-distance (v) not correct? How did you arrive at this conclusion?
  (c) Choose an appropriate scale to draw a ray diagram for the observation at S. No. 4 and find the approximate value of magnification. VIEW SOLUTION

• Question 24
  (a) Define the following terms in the context of spherical mirrors : 
   

  (i) Pole
  
  (ii) Centre of curvature
  
  (iii) Radius of curvature
  
  (iv) Principal axis

  
  (b) Draw ray diagrams to show the principal focus of (i) a concave mirror, and (ii) a convex mirror.
  
  (c) In the following diagram. MM' is a concave mirror and AB is an object. Draw on your answer-sheet a ray diagram to show the formation of image of this object.
  
  VIEW SOLUTION