physics ONLINE TEST

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12th Physics One Mark Test – Full

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-St. Joseph Study Centre

 

1 / 90

When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts as a plane sheet of glass. This implies that the liquid must have refractive index?

2 / 90

Which of the following is a secondary cell?

3 / 90

When a metallic surface is illuminated with radiation of wavelength λ , the stopping potential is V. If the same
surface is illuminated with radiation of wavelength 2λ , the stopping potential is V / 4. The threshold wavelength for the metallic surface is?

4 / 90

In a series resonant RLC circuit, the voltage across 100 Ω resistor is 40 V. The resonant frequency ω is 250 rad/s. If the value of C is 4 μF, then the voltage across L is?

5 / 90

A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m then?

6 / 90

The time taken by the radioactive element to reduce to 1 / e times is?

7 / 90

The speed of light in an isotropic medium depends on?

8 / 90

The particle size of ZnO material is 30 nm. Based on the dimension it is classified as?

9 / 90

In an electron microscope, the electrons are accelerated by a voltage of 14 kV. If the voltage is changed to 224 kV, then the de Broglie wavelength associated with the electrons would?

10 / 90

A light source of wavelength 520 nm emits 1.04 × 10¹⁵ photons per second while the second source of 460 nm
produces 1.38 × 10¹⁵ photons per second. Then the ratio of power of second source to that of first source is?

11 / 90

What is the ratio of the charges |q₁/q₂| for the following electric field line pattern?

12 / 90

A photoelectric surface is illuminated successively by monochromatic light of wavelength λ and λ/2 . If
the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the material is?

13 / 90

The zener diode is primarily used as?

14 / 90

Electromagnetic induction is not used in?

15 / 90

Electromagnetic wave are?

16 / 90

A parallel plate air capacitor is charged to a potential difference of V volt. On disconnecting the charging battery distance between the plates of the capacitor is increased using an insulting handle. As a result the potential difference between the plates?

17 / 90

Two point white dots are 1 mm apart on a black paper. They are viewed by eye of pupil diameter 3 mm approximately. The maximum distance at which these
dots can be resolved by the eye is, [take wavelength of light, λ = 500 nm]

18 / 90

The mass of a ⁷₃Li nucleus is 0.042 u less than the sum of the masses of all its nucleons. The average binding energy per nucleon of ⁷₃Li nucleus is nearly?

19 / 90

If the velocity and wavelength of light in air is Vₐ and λₐ and that in water is Vw and λw, then the refractive index of water is?

20 / 90

Avalanche breakdown is primarily dependent on the phenomenon of?

21 / 90

For light incident from air on a slab of refractive index 2, the maximum possible angle of refraction is?

22 / 90

A carbon resistor of (47 ± 4.7 ) k Ω to be marked with rings of different colours for its identification. The colour code sequence will be?

23 / 90

An air bubble in glass slab of refractive index 1.5 (near normal incidence) is 5 cm deep when viewed from one surface and 3 cm deep when viewed from the opposite face. The thickness of the slab is?

24 / 90

An object is placed in front of a convex mirror of focal length of f and the maximum and minimum distance of
an object from the mirror such that the image formed is real and magnified?

25 / 90

Atomic number of H – like atom with ionization potential 122.4 v for n = 1 is?

26 / 90

Of the following devices, which has small resistance?

27 / 90

The materials used in Robotics are?

28 / 90

The following graph shows current versus voltage values of some unknown conductor. What is the resistance of this conductor?

29 / 90

Two identical conduction balls having positive charges q₁ and q₂ are separated by a center to center distance r. If they are made to touch each other and then separated to the same distance, the force between them will be?

30 / 90

A piece of copper and another of germanium are cooled from room temperature to 80 K. The resistance of ?

31 / 90

The forbidden energy gap for germanium is of the order of?

32 / 90

In a tangent galvanometer, for a constant current, the deflection is 30°. The plane of the coil is rotated through 90°. Now, for the same current, the deflection will be?

33 / 90

Light transmitted by Nicol prism is,?

34 / 90

The speed of electromagnetic waves in independent of?

35 / 90

The period of revolution of a charged particle inside a cyclotron does not depend on?

36 / 90

A toaster operating at 240 V has a resistance of 120 Ω. The e power is?

37 / 90

A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A the efficiency of the transformer is approximately?

38 / 90

If the potential of a capacitor having capacity 6µF is increased from 10 V to 20 V, then increase in its energy will be?

39 / 90

An inductor 20 mH, a capacitor 50 μF and a resistor 40 Ω are connected in series across a source of emf V = 10 sin 340 t. The power loss in AC circuit is?

40 / 90

When the number of turns (n) in a galvanometer is doubled current sensitivity?

41 / 90

The nuclear force is due to the continuous exchange of particles called?

42 / 90

What is the angle between the electric dipole moment and the electric field strength due to it on the equatorial line?

43 / 90

The variation of frequency of carrier wave with respect to the amplitude of the modulating signal is called?

44 / 90

Which of the following statement is false for the properties of electromagnetic waves?

45 / 90

If the length of a copper wire has a certain resistance R then on doubling the length its specific resistance?

46 / 90

Nichrome wire is used as the heating element because it has?

47 / 90

In J.J. Thomson e/m experiment, a beam of electron is replaced by that of muons (particl with same charge as that of electrons but mass 208 times that of electrons). No deflection condition is achieved only if?

48 / 90

The dimension of 1 / μ₀ℇ₀ is?

49 / 90

In a Young’s double-slit experiment, the slit separation is doubled. To maintain the same fringe spacing on the screen, the screen-to-slit di stance D must be changed to,?

50 / 90

The electric and magnetic fields of an electromagnetic wave are?

51 / 90

The alloys used for muscle wires in Robots are?

52 / 90

The coefficient of self induction of a solenoid is independent of?

53 / 90

The work function of aa metal is 3.5 eV. If the stopping potential is -1.2 volt then the energy of the incident photon is?

54 / 90

The total electric flux for the following closed surface which is kept inside water?

55 / 90

In CE single stage amplifier, the voltage gain at mid – frequency is 10. The voltage gain at upper cut off frequency is?

56 / 90

When light is incident on a soap film of thickness 5×10⁻⁵ cm, the wavelength of light reflected maximum in the visible region is 5320 Å. Refractive index of the film will be,?

57 / 90

The unit of reduction factor of tangent galvanometer is?

58 / 90

An electric dipole is placed at an alignment angle of 30° with an electric field of 2 x 10⁵ NC¯¹. It experiences torque equal to 8 Nm. The charge on the dipole if the dipole length is 1cm is? 

59 / 90

In a transformer, the number of turns in the primary and the secondary are 410 and 1230 respectively. If the current in primary is 6A, then that in the secondary coil is?

60 / 90

Two coherent monochromatic light beams of intensities I and 4I are superposed. The maximum and minimum possible intensities in the resulting beam are?

61 / 90

“Ski wax” is an application of nano product in the field of?

62 / 90

The spectral series of hydrogen atom in UV region are called?

63 / 90

A current loop in a magnetic field?

64 / 90

Fraunhofer lines are an example of _______ spectrum?

65 / 90

The barrier potential of a silicon diode is approximately,?

66 / 90

The torque on a rectangular coil placed in a uniform magnetic field is large when?

67 / 90

A plane glass is placed over a various coloured letters (violet, green, yellow, red) The letter which appears to be raised more is,?

68 / 90

First diffraction minimum due to a single slit of width 1.0×10⁻⁵ cm is at 30⁰. Then wavelength of light used is,?

69 / 90

The principle based on which a solar cell operates is?

70 / 90

A step-down transformer reduces the supply voltage from 220 V to 11 V and increase the current from 6 A to 100 A. Then its efficiency is?

71 / 90

The explosion of an atom bomb is based on the principle of?

72 / 90

A ray of light strikes a glass plate at an angle 60⁰. If the reflected and refracted rays are perpendicular to each other, the refractive index of the glass is,?

73 / 90

A ray of light travelling in a transparent medium of refractive index n falls, on a surface separating the medium from air at an angle of incidents of 45º. The ray can undergo total internal reflection for the following n?

74 / 90

Which of the following electromagnetic radiations is used for viewing objects through fog?

75 / 90

The colour of light emmitted by a LED depends on?

76 / 90

The threshold wavelength for a metal surface whose photoelectric work function is 3.313 eV is ?

77 / 90

Which charge configuration produces a uniform electric field?

78 / 90

A wire connected to a power supply of 230 V has power dissipation P₁ . Suppose the wire is cut into two equal pieces and connected parallel to the same power supply. In this case power dissipation is P₂. The e ratio P₂ / P₁ is ?

79 / 90

The time taken by the radioactive element to reduce to 1 / e times is?

80 / 90

A positively charged particle moving due east enters a region of uniform magnetic field directed vertically upwards. The particles will?

81 / 90

Two identical point charges of magnitude – q are fixes as shown in the figure below. A third charge + q is placed midway between the two charges at the point P. Suppose this charge + q is displaced a small distance from the point P in the direction indicated by the arrows, in which direction(s) will + q be stable with respect to the displacement?

82 / 90

In a hydrogen atom, the electron revolving in the fourth orbit, has angular momentum equal to?

83 / 90

A metal foil of negligible thickness is introduced between two plates of a capacitor at the centre. The capacitance of capacitor will be?

84 / 90

Torque on a dipole in a uniform electric field is maximum when angle between p and E is

85 / 90

The half-life period of a radioactive element A is same as the mean life time of another radioactive element B. Initially both have the same number of atoms. Then?

86 / 90

Two radiations with photon energies 0.9 eV and 3.3 eV respectively are falling on a metallic surface successively. If the work function of the metal is 0.6 eV, then the ratio of maximum speeds of emitted electrons in the two cases will be ?

87 / 90

A circle of radius r is drawn with charge +q at the centre. A charge q˳ is moved between two point on the circle. Then work done is?

88 / 90

Which of the following is false for electromagnetic waves?

89 / 90

When the current changes from +2A to −2A in 0.05 s, an emf of 8 V is induced in a coil. The co-efficient of self-induction of the coil is?

90 / 90

A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that
its end closer to the pole is 20 cm away from the mirror. The length of the image is?

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