Board Paper of Class 10 2012 Science (SET 3) - Solutions

Write the name and formula of the first member of the carbon compounds having functional group − CHO.

State one role of ciliary muscles in the human eye.

Write the name and formula of a molecule made up of three atoms of oxygen.

Name two decomposers operating in our ecosystem.

Why do all the elements of the (a) same group have similar properties, (b) same period have different properties?

An element E has following electronic configuration:

(a) To which group of the periodic table does element E belong?

(b) To which period of the periodic table does element E belong?

(c) State the number of valence electrons present in element E.

(d) State the valency of the element E.

Why is vegetative propagation practiced for growing some types of plant? List two plants which are grown by this method.

State the role of placenta in the development of embryo.

To construct ray diagram we use two light rays which are so chosen that it is easy to know their directions after reflection from the mirror. List these two rays and state the path of these rays after reflection. Use these rays to locate the image of an object placed between centre of curvature and focus of a concave mirror.

What is the colour of the clear sky during day time? Give reason for it.

Draw a labeled ray diagram to illustrate the dispersion of a narrow beam of white light when it passes through a glass prism.

List the products of combustion of fossil fuels. What are their adverse effects on the environment?

List three problems which arise due to construction of big dams. Suggest a solution for these problems.

State the meaning of inherited traits and acquired traits. Which of the two is not passes on the next generation? Explain with the help of an example.

How are fossils formed? Describe, in brief, two methods of determining the age of fossils.

If we pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant we will get pea plants of F₁ generation. If we now self-cross the pea plant of F₁ generation, then we obtain pea plants of F₂ generation.

(a) What do the plants of F₂ generation look like?

(b) State the ratio of tall plants to dwarf plants in F₂ generation.

(c) State the type of plants not found in F₁ generation but appeared in F₂ generation, mentioning the reason for the same.

A 5 cm tall object is placed perpendicular to the principle axis of a convex lens of focal length 12 cm. The distance of the object from the lens is 8 cm. Using the lens formula, find the position, size and nature of the image formed.

State the types of mirrors used for (i) headlights and (ii) rear view mirror, in cars and motorcycles. Give to justify your answer in each case.

An old man cannot see objects closer than 1 m from the eye clearly. Name the defect of vision he is suffering from. How can it be corrected? Draw ray diagram for the (i) defect of vision and also (ii) for its correction.

Name the oxidizing agent used for the conversion of ethanol to ethanoic acid. Distinguish between ethanol and ethanoic acid on the basis of (i) litmus test, (ii) reaction with sodium hydrogen carbonate.

List and explain in brief three methods of contraception.

Na, Mg and Al are the elements having one, two and three valence electrons respectively. Which of these elements (i) has the largest atomic radius, (ii) is least reactive? Justify your answer stating reason for each.

List the new Cartesian sign convention for reflection of light by spherical mirror. Draw a diagram and apply these conventions for calculating the focal length and nature of spherical mirror which forms a 1/3 times magnified virtual image of an object placed 18 cm in front of it.

OR

With the help of a ray diagram, state what is meant by refraction of light. State Snell’s law for refraction of light and also express it mathematically.

The refractive index of air with respect to glass is 2/3 and the refractive index of water with respect to air is 4/3. If the speed of light in glass is 2 × 10⁸ m/s, find the speed of light in (a) air, (b) water.

What are hydrocarbons? Write the name and general formula of (i) saturated hydrocarbons, (ii) unsaturated hydrocarbons, and draw the structure of one hydrocarbon of each type. How can an unsaturated hydrocarbon be made saturated?

OR

What are detergents chemically? List two merits and two demerits of using detergents for cleansing. State the reason for the suitability of detergents for washing, event in the case of water having calcium and magnesium ions.

Distinguish between unisexual and bisexual flowers giving one example of each. Draw a diagram showing process of germination of pollen grains on stigma and label the following parts:

(a) Female germ cell

(b) Male germ cell

(c) Ovary

OR

Draw a diagram of human female reproductive system and label the part.

(i) That produces eggs.

(ii) Where fusion of egg and sperm take place.

(iii) Where zygote is implanted.

What happens to human egg when it is not fertilized?