Assignment of SCIENCE of class 9th
1. What is the least distance of distinct vision of a normal human eye ?
2. Name the muscle responsible for bringing change in the focal length of the eye lens?
3. Name one defect of vision which cannot be corrected by any type of spectacle lenses ?
4. State one effect produced by the scattering of light by the atmosphere ?
5. What is the nature of image formed on the retina of the eye ?
6. What type of lens is used for correcting hypermetropia ?
7. Who was the first person to obtain the spectrum of sunlight ?
8. What is the function of optic nerve in human eye ?
9. What is range of vision ?
10.Why do different colours deviate through different angles on passing through a prism?
11.As light rays pass from air into glass prism, are they refracted towards or away from the
normal ?
12.Which color has largest wavelength ?
13.Which defect of vision can be rectified using a concave lens ?
14.What phenomenon causes twinkling of star on a clear night ?
15.What is meant by scattering of light ?
16.Why does the sky appear black instead of blue to an astronaut?
17.What is the basic cause of atmospheric refraction?
18.Why does clear sky look blue?
19.Can visible light be scattered by atoms/molecules in earth's atmosphere?
20.What is a spectrum?
21.Name the defect of vision in person
a. Whose near point is more than 25cm away?.
b. Whose far point is less than infinity
22.A person can see only objects beyond lm. From his eyes. Name the defect of the eye.
23.Out of light of blue and red colours which one is scattered most?
24.What is the function of crystalline lens in the human eye?
25.Which phenomenon is responsible for increasing the apparent length of the day by 4
minute?
26.What is the far point of a person suffering from Myopia.
27.What name is given to front transparent part of human eye?
28.Where do we see :(1) Concave and (2) Convex lens in bifocal lenses.
29.What is the nature of image formed by our eye?
30.Name the liquid which is present between eye lens and cornea.
31.Where does most of the refraction of light in an eye occurs?
32.Which kind of lens is an eye lens?
33.What is the cause of dispersion of light?
34.Under very dim light, we are able to see the objects but cannot distinguish between
colours why?
35.What is the range of vision for normal human eye ?
36.How is the amount of light entering the eye controlled ?
37.What is the colour of danger signal? Why?
38.What is rainbow? How is rainbow formed?
39.State two causes of myopic vision.
40.How an uncorrected myopic eye sees far off objects.
41.What is presbyopia? Name the type of lens which can be used to correct presbyopia.
42.Explain why planet do not twinkle at night?
43.Explain about the colour of the sun at sunrise and sunset.
44.Define the term (1) Near point (2) Far point
45.Why is a normal eye not able to see clearly the object closer than 25 cm.
46.Draw a ray diagram to show the refraction of light through a glass prism on the diagram
mark. (a) Incident ray (b) Emergent ray and (c) Angle of deviation
47.How is the dispersed white light recomposed ?
48.The near point of a hypermetropic eye is at 75 cm from the eye. What is the power of
the lens required to enable him to read clearly a book held at 25 cm from the eye
ACID, BASE AND SALTS…..
1.How does baking powder differ from baking soda? (1 mark)
2.What will happen if heating is not controlled while preparing plaster of Paris. (1 mark)
3.Name two organic acids. (1 mark)
4.A housewife found that the cake prepared by her is hard and small in size. Which
ingradient has she
forgotten to add that would have made the cake fluffy. Give reason. (2 marks)
5.What is water of crystallization? Name two hydrated salts. (2 marks)
6.What happens when an acid reacts with a base? Give equation of the reaction of
the reaction involved. What is the special name of this reaction? (2 marks)
7.Explain how pH change in the river water can endanger the lives of aquatic animals. (2
marks)
8.A baker found that the cake prepared by him is hard and small in size. Which ingredients
has he forgotten
to add that would have caused the cake to rise and become light? (2 marks)
9.What are the two main ways in which common salt (sodium chloride) occurs in
nature? How is common salt obtained from sea water? Explain. (3 marks)
10. What happens when (3 marks)
(a)Solid sodium hydrogen carbonate is heated,
(b)Chlorine gas is passed through dry slaked lime,
(c)Gypsum is heated to a temperature of 373 K?
11.(i) What is a salt? (5 marks)
(ii) Why aqueous solution of sodium carbonate is basic in nature?
(iii)Why is an aqueous solution of ammonium chloride acidic in nature?
12.A milkman adds a very small amount of baking soda to fresh milk
13.Why do acids not show acidic behaviour in the absence of water?
14.Alcohols and Glucose contain hydrogen but are not categorized as acids.
15.Plaster of Paris should be stored in a moisture-proof container. Explain why?
16.Why is calcium sulphate hemihydrates called 'Plaster of Paris'?
17.Name a solution reacts with crushed egg-shells to give a gas that lime-water milky.
18.Why does distilled water not conduct electricity, whereas rain water does.
19. Define aqua-regia, efflorescence
20.Name the sodium compound which is used for softening hard water.
21.Why should curd and sour substances not be kept in brass and copper vessels?
22.What are the components of baking powder?
23.Three solutions A, B and C have pH, values of 6, 4 and 10 respectively. Which of the
solution is highly acidic?
24.Two solutions X and Y have pH = 4 and pH = 8 respectively. Which solution will give
alkaline reaction and which one acidic.
25.A farmer has found that the pH of soil in his fields is 4.2. Name any two chemical
materials which he can mix with soil with soil to adjust its pH.
26.State the chemical name and formula of common salt. (1 mark)
27.‘Sweet tooth’ may lead to tooth decay. Explain why? What is the role of tooth paste in
preventing cavities?
28.Write the reaction that takes place when sodium oxide reacts with water. How will this
solution behave towards phenolphthalein and red litmus paper? (2 marks)
29.Why should curd and sour substances not be kept in brass and copper vessels?
30.How is the concentration of hydronium ions (H2O+) affected when a solution of an acid
is diluted? (2 marks)
31.Why do acids not show acidic behavior in the absence of water? (2 marks)
32.Identify the compound of calcium which is used for plastering of fractured bones. With
the help of chemical equation, describe how this compound is prepared. What special
precaution should be taken during the preparation of this compound?
33.State Arrhenius Concept of acids and bases. Giving reason, select a strong acid and a
weak base from amongst the following substances: (3 marks) H2CO3, HNO3, NaOH, NH4OH
34.(i) Why should curd and sour substances no be kept in brass and copper vessels.
(ii) The pH of hydrochloric acid solution is 3. Does it mean that it has only hydronium ions. If
not, how are OH- ions generated?
(iii) Distinguish between acid and alkali.
35.Compounds like alcohol and glucose also contain hydrogen but are not categorized as
acids. Describe an activity to prove it.