Class – X (CBSE) F.M -100
Section -A
Choose the correct alternative (MCQ) : 1 x 25 = 25
1. A convex lens and a concave lens having focal lengths 10 cm and 20 cm respectively are placed in contact with each other . Which of thefollowing statements is correct about the lens combination ?
A) It will behave likea plane glass slab
B) It will behave like a convex lens
C) It will behave like a concave lens
D) It will behave vlike a cylindrical lens
2. The part of eye which causes change in the focal length of eye lens to provide it exceptional accommodation power is :
A) Aqueous humour B) Ciliary muscles C) Pupil D) Iris
3. Pushkar was studying a light phenomenon and wrote down the following statements in that contex :
i) A concave mirror can be used as a shaving mirror because it can form an enlarged , virtual image when object is placed between the pole and focus .
ii) A convex lens always forms real , inverted images , regardless of the position of the object .
iii) The relationship between object distance (u) , image distance (v) and the focal length (f) of the lens is given by 1/f = 1/v - 1/u
Choose the option enlisting all the correct statements :
A) I ) and ii) B) i) and iii) C) ii) and iii) D) I) , II) and iii)
4. During a lab experiment , Bhavna uses a solenoid connected to a battery . She note down the following facts :
i) The pattern of the magnetic field lines inside the solenoid is similar to a bar magnet . Ii) The north pole and south pole of the current – carrying solenoid can be identified by applying the right hand rule . Iii) A solenoid can be used to magnetise a piece of a soft iron making it an electromagnet .
Choose the option enlisting all the correct statements :
A) i) and iii) B) ii) and iii) C) i) and ii) D) i) , ii) and iii)
5. When a convergent beam of light is incident on a convex mirror , the reflected rays appear to be coming from 20cm behind the mirror and retrace their path . The focal length of the mirror is
A) 20 cm B) 10 cm C) 40 cm D) 30 cm
6. In the above diagram the values of bthe angle of incidence and the angle of reflection are :
A) I = 50 ° , r = 40° B) i = 40° , r = 50° C) i = 40° r = 40° D) I = 50° r = 50°
7. An object is placed at a distance of 0.25 m in front of a plane mirror . The distance between the object and image will be – A) 0.25 m B) 1.0 m C) 0.5 m D) 0.125 m
8. An object at a distance of 30 cm from a concave mirror gets its image at the same point . The focal length of the mirror is A) - 30 cm B) 30 cm C) - 15 cm D) 15 cm
9. The least resistance obtained by using 2 Ω , 4 Ω , 1 Ω and 100 Ω is
A) < 100 Ω B) < 4 Ω C) < 1 Ω D) > 2 Ω
10. Work of 14 J is done to move 2 C charge between two points on a conducting wire . What is the potential difference between the two points ?
A) 28 V B) 14 V C) 7 V D) 3.5 V
11. Electrical resistivity of a given metallic wire depends upon -
A) its length B) its thickness C) its shape D) Nature of the material
12. What is the relationship between resistance and current ?
A) They are directly related to each other
B) They are inversely related to each other
C) The resistance has a greater magnitude than the current
D) The current has a greater magnitude than the resistance
13. Which of the following represents voltage ?
A) Work done / Current x time B) work done x Charge C) Work done x time / Current D) Work done x Charge x Time
14. A coil in the heater consumes power P on passing current . If it is cut into halves and joined in parallel , it will consume power A) P B) P/2 C) 2P D) 4P
15. The most suitable material for making the core of an electromagnet is :
A) Steel B) Iron C) Soft Iron D) Aluminium
16. When a staright conductor is carrying current :
A) There are circular magnetic field lines around it
B) There are magnetic field lines parallel to the conductor
C) There are no magnetic field lines
D) None of the above
17. The magnetic field lines inside a straight solenoid carrying current :
A) is zero B) Decrease as we move towards its end C) Is the same at all points D) Increase as we move towards its end
18. The force on a current carrying conductor when placed perpendicular in a uniform magnetic field . A) F = BIL B) F = B/IL C) F = L/BI D) F = I/BL
19. A soft iron bar is introduced inside a current-carrying solenoid . The magnetic field inside a solenoid : A) Decrease B) Will increase C) Will become zero D) Will remain unaffected
20. In which part of the human eye is the image of an object formed ?
A) Iris B) Pupil C) Retina D) Cornea
21. The splitting of white light into different colours on passing through a prism is called A) Reflection B) Refraction C) Dispersion D) deviation
22. What lens is used to correct myopia (short-sightedness )?
A) Convex lens B) Concave lens C) Bifocal lens D) Cylindrical lens
23. Which colour bends the most when white light passes through a glass prism ?
A) Red B) Yellow C) Violet D) Green
24. Why does the clear sky appear blue ?
A) Blue light absorbed by the atmosphere B) Blue light scatters the most C) Red light scatters the most D) Ocean water reflect blue light
25. The danger signals installed at the top of tall buildings are red in colour . This can be easily seen from a distance because among other colours , the red light
A) is scattered the most by smoke or fog
B) is scattered the least by smoke or fog
C) is absorbed the most by smoke or fog
D) moves faster in the air
Section – B
From Q 26 to Q 31 carries 2 mark each ( 2x 6 =12 ) and from Q32 to Q37 carries 3 mark each ( 3x 6 = 18)
26. What is the magnification of images formed by plane mirrors and why ? 2
27. Draw a labelled ray diagram to show the path of the reflected ray corresponding to an incident ray of light parallel to the principal axis of a convex mirror . Mark the angle of incidence and angle of reflection . 2
28. state Ohms law and explain . 2
29. List three factors on which the resistance of a conductor depends . 2
30. If the field lines of a magnetic field are crossed at a point , what does it indicate ? 2
31. List the two causes of hypermetropia . 2
32 .What eye defect is myopia ? Describe with neat diagram how this defect of vision can be corrected by suitable lens . 3
33. List two possible ways in which a concave mirror can produce a magnified image of an object placed in front of it . State the difference if any between these two images . 3
34. The absolute refractive indices of glass and water are 4/3 and 3/2 respectively . If the speed of light in glass is 2 x 10^8 m/s , calculate the speed of light in vacuum , water . 3
35. Calculate the resistivity of the material of a wire of length 1.0 m ,radius 0.01 cm and resistance 20 ohms . 3
36. State the three factors on which the strength of magnetic field mproduced by a current carrying solenoid depends . 3
37. Write about power of accommodation of human eye . Explain why the image distance in the eye does not change when we change the distance of an object from the eye ? 3
Section – C
Following questions( Q38 to Q42) consist of two statements – Assertion(A) and Reason (R) . Answer these questions selecting the appropriate option given below :
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true
38. Asserion (A) : The emergent ray is parallel to the direction of the incident ray .
Reason (R) : The extent of bending of the ray of light at the opposite parallel faces ( air-glass interface and glass-air interface ) of the rectangular glass slab is equal and opposite . 1
39. Assertion(A) : Light travels faster in glass than in air .
Reason (R) : Glass is denser than air . 1
40. Assertion (A) : A current–carrying wire does not get electrically charged .
Reason(R) : The electric current in a metal wire is due to the flow of free electrons , where the total number of protons in the wire is equal to the total number of electrons . 1
41. Assertion( A) : If a graph is plotted between the potential difference and the current flowing .
Reason( R) : The current is directly proportional to the potential difference . 1
42 . Assertion(A) : As the speed of the coil in the motor increases , there is a reduction in the current flowing through it .
Reason (R) : During rotation in an electric motor , some induced current is produced. 1
Section –D
Read the passage and the questions that follow : 5
43 . An electric iron is a home appliance that uses electricity to produce heat . Inside iron , there is a heating element made of a high – resistance material like nichrome wire . When a voltage( V) is applied across the ends of this wire , an electric current (I) flows through it . The rate at which electrical energy is used up is called electric power (P) .A typical household electric iron has a rating of 1000 W , 220V stamped on it , meaning it consumes 1000 joules of energy every second when connected to a 220 V supply .
i) What is the meaning of the rating 1000 W , 220V on an electric appliance ? 1
ii) Calculate the electric current (I) flowing through the iron when it is connected to the 220 V mains . 1
iii) Find the resistance (R) of the heating element on the electric iron . 1
iv) How much electrical energy( in kWh) is consumed if the electric iron is used for 2 hours daily over a period of 30 days ? 2
Section – E
This section has 7 questions with 5 marks for each question .
44. A convex lens has a focal length of 10 cm . At what distance from the lens should the object be placed so that it forms a real and inverted image 20 cm. Away from the lens ? What would be the size of the image formed if the object is 2 cm high ? With the help of a ray diagram show the formation of the image by the lens in this case ? 5
45 . Draw a ray diagram to show the use of a convex lens for the formation of images having the following characteristics .
a) Real and inverted and diminished b) Virtual , erect & magnified 5
46. Explain parallel combination of resistors and derive the formula for equivalent resistance . 5
47. A) Write the mathematical expression for Joules law of heating . B) Compute the heat generated while transferring 96000 coulomb of charge in two hours through a potential difference of 40 V . 5
48. Make a diagram to show how hypermetropia is corrected . The near point of a hypermetropic eye is 1 m . What is the power of the lens required to correct this defect ? Assume the near point of the normal eye is 25 cm . 5
49. Explain the principle , construction and working of an electric motor with the help of a leveled diagram . 5
50 .Differentiate between refraction , dispersion and scattering of light with specific o example for each phenomenon . 5
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