Human Eye And colorful World class 1oth imp questions

 "Om Sai Ram"

Topic :-Human Eye And colorful World

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. Draw a neat labelled diagram showing the refraction of light through a glass prism.

23. The sun is seen a few minutes before actual sunrise and after actual sun set. Explain why?

24. The sky appears black when viewed from the surface of moon. Explain why?

25. Why danger signals are of Red colour?

26. Why sun appears reddish during sunrise and sunset?

27. The setting sun is more reddish than rising sun. Explain why?

28. What is persistence of vision? How does it help us in seeing motion pictures?

29. What are primary colors?

30. Why planets do not twinkle?

31. What is total internal reflection?

32. What is cataract? How is it corrected?

33. Define far point. What is its value for a normal human eye?

34. What is dispersion?

35. Draw a neat diagram to show the dispersion of light when passed through a glass prism.

36. How is rainbow formed?

37. If you see a rainbow in the morning, in which direction of the sky will you see it?

38. What is scattering?

39. Explain the blue colour of sky?

40. Why clouds are white?

41. A red coloured piece of glass appears white when it is ground. Explain why?

42. What is Tyndal effect?

43. Write the constituent colours of white light in order of increasing wavelength.

44. When you enter a dark room from sunlight, you cannot see things for a while and after sometime you start seeing things. Explain this observation.

45. Why do stars twinkle?
Add : CL 157 D.D Nagar Gwalior Mob.:9039803981

worksheet class 10 Light

                                                  "Om Sai Ram"      

                                 Worksheet of Light

1. You are given kerosene, turpentine oil and water. In which of these does the light ray

travel fastest? Given refractive index of kerosene = 1. 44, Refractive index of

turpentine 1· 47, refractive index of water = 1· 33.

2. Under what condition a convex lens when placed in a medium behaves as an ordinary

glass plate?

3. Light having a free space wavelength λ= 500 nm passes from vacuum into diamond

having refractive index 2.4. What would be the wavelength of light in the diamond?

4. A ray of light is travelling in water medium falls on the water-air interface at an angle

of 45° with the vertical. Will it be possible by the ray of light to come out of the water

surface?

5. A virtual image cannot be focused on a screen.” this statement appears to be

contradictory as we focus a virtual image onto a screen, i. e retina explain it.

6. In what way is the word AMBULANCE painted in front of the hospital vans? Why is it painted this way?

7. A concave mirror and convex lens are held in water. What change, if any, do you

expect to find in the focal length of either?

8. ‘ Vehicles in this mirror are closer than they appear’. This warning is printed on the

convex mirror outside the driver’s side of a vehicle. What is the reason for this warning?

9. A glass tumbler is placed over a coin and filled with water. Coin disappears after

sometime when seen from the sides of the tumbler. Give suitable name for the

phenomena observed.

10. If a lens has been blackened in strips, what will be the difference in the nature of the

image?

11. How many images are seen when two mirrors are placed in parallel?

12 . Is it possible for a lens to act as a convergent in one medium and divergent in another?

13. What happens to the image distance in the eye when we increase the distance of an

object from the eye?

14. A student has difficulty in reading the black board while sitting in the last row. What

would be the defect the student is suffering from? How can it be corrected?

15. A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should

be the nature of the corrective lens used to restore proper vision?

16. A person is able to see objects clearly only when these are lying at distances

Between 50 cm and 300 cm from his eye.

(a) What kind of defects of vision is he suffering from?

(b) What kind of lenses will be required to increase his range of vision from 25 cm to

infinity? Explain briefly.

17. A beam of white light is passed through a hollow prism, will it produce a spectrum?

18. Do all people looking at a star, locate it at the same apparent position? If not explain.

19. When a torch light is focussed on the eye which cells get activated immediately?

a) Sensory cells b) light sensitive cells

c) Cells of the ciliary muscles d) cells at the blind spot

20. The defect in vision developed due to gradual weakening of ciliary muscle and diminishing

flexibility of eye lens is:

a) Myopia b) hypermetropia c) night blindness d) presbyopia

MCQ work, Energy and power class 9

                                                                         "Om Sai Ram"

MCQ Of Work And Energy

1. When a body falls freely towards the earth, then its total energy

(a) increases

(b) decreases

(c) remains constant

(d) first increases and then decreases

2. A car is accelerated on a levelled road and attains a velocity 4 times of its initial velocity. In this process the potential energy of the car

(a) does not change

(b) becomes twice to that of initial

(c) becomes 4 times that of initial

(d) becomes 16 times that of initial

3. In case of negative work the angle(in degree) between the force and displacement is

(a) 0 (b) 45 (c) 90 (d ) 180

4. An iron sphere of mass 10 kg has the same diameter as an aluminium sphere of mass is 3.5 kg. Both spheres are dropped simultaneously from a tower. When they are 10 m above the ground, they have the same

(a) acceleration

(b) momentum

(c) potential energy

(d) kinetic energy

5. A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational force will be (g =10 m s–2)

(a) 6 ×103 J

(b) 6 J

(c) 0.6 J

(d) zero

6. Which one of the following is not the unit of energy?

(a) joule

(b) newton metre

(c) kilowatt

(d) kilowatt hour

7. The work done on an object does not depend upon the

(a) displacement

(b) force applied

(c) angle between force and displacement

(d) initial velocity of the object

8. Water stored in a dam possesses

(a) no energy

(b) electrical energy

(c) kinetic energy

(d) potential energy

9. A body is falling from a height h. After it has fallen a height h/2 , it will possess

(a) only potential energy

(b) only kinetic energy

(c) half potential and half kinetic energy

(d) more kinetic and less potential energy

10. How are Joule (J) and ergs (erg) related?

(a) 1J = 10⁷ erg (b) 1erg = 10 ^-7J (c) 1J = 10^-7 erg (d) None

Floatation class 9th important questions

Om Sai Ram
SPECTRUM CLASSES

Floatation

1. Give reason why, a block of plastic when released under water comes up to the surface of water.

Ans: It is because of buoyancy force

2. Define density. What is the SI unit of density?

Ans: Mass per unit volume of a substance is called density.

The SI unit of density is kg/m3 or gm/cm3

3. Name and define SI unit of pressure.

Ans: Pascal or Newton/square meter

1 Pascal is the pressure act when 1 N  force acts perpendicular on unit area.

4. What do you understand by the term buoyancy?

Ans: Tendency of fluid to exert an upward force when a body is immersed in to it is called buoyancy

5. Why does a mug full of water feel lighter inside water?

Ans: a mug full of water feels lighter inside water because of buoyancy force

6. A perpendicular force of 50 N acting on a surface generates a pressure of 250 Pa. Calculate the area of cross-section of the surface on which pressure is acting.

Ans: p = F/A , A = F/p = 50 N/250 Pa = 0.2 m²

7. What is a lactometer used for?

Ans: lactometer used for finding purity of milk

8. State the unit of density and relative density in SI system.

Ans: The unit of density is  kg/m3

There is no unit of relative as it is ratio of same physical quantity.  

9. State Archimedes’ principle.

Ans: When a body is immersed partially or completely in a fluid (liquid or gas), it experiences an up thrust or buoyant force which is equal to the weight of the fluid displaced by the body.

10. What is meant by buoyant force?

Ans:  if a body is immersed partially or completely in a fluid, it experiences an up thrust called buoyant force.

11. A cork floats while the nail sinks in water. Give reason.

Ans: Weight of cork is  less than buoyant force acting on it so it floats Where as : Weight of the nail  is  more than buoyant force acting on it so it sink

12. What is the principle of floatation?

Ans: A body floats is a liquid if weight of the liquid displaced by the immersed portion of the body is equal to the weight of the body.

13. A body of mass 400 g has a volume of 300 cm³. Will body sink in water or not? [Density of water = 1000 kgm–3]

Ans:  density of body =m/v= 400/300=1.3gm/cm3 which is greater than density of water 1gm/cm3 Hence, Body will  sink in water.

14. When we stand on loose sand, our feet go deep into the sand. But when we lie down on the sand our body does not go that deep in the sand. Why?

Ans: when we lie down on the sand our body exert same force on large are that reduce pressure and our body does not go that deep in the sand.

15. Why is it easy to walk on sand with flat shoes, then with high heel shoes?

Ans: flat shoes exert force on large surface area and less force act on sand this make easy to walk on sand
Er.Shyam Pachori 
CL 157 D.D Nagar 
Mob.:9039803981