#### 12th Standard Physics English Medium Free Online Test Volume 2 One Mark questions with Answer Key 2020

12th Standard

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Physics

Time : 00:25:00 Hrs
Total Marks : 25
25 x 1 = 25
1. 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,

(a)

n = 1.25

(b)

n = 1.33

(c)

n = 1.4

(d)

n= 1.5

2. One of the of Young’s double slits is covered with a glass plate as shown in figure. The position of central maximum will,

(a)

get shifted downwards

(b)

get shifted upwards

(c)

will remain the same

(d)

data insufficient to conclude

3. A plane mirror produces a magnification of

(a)

-1

(b)

+ 1

(c)

Zero

(d)

Between 0 and + ∞

4. A plane mirror is placed at the bottom of the tank containing a liquid of refractive index J.1.P is a small object at a height h above the mirror, an observer O-vertically above P outside the liquid. See p and its image in the mirror. The apparent distance between these two will be

(a)

$2\mu h$

(b)

$\cfrac { 2h }{ \mu }$

(c)

$\cfrac { 2h }{ \mu -1 }$

(d)

$h\left( 1+\cfrac { 1 }{ \mu } \right)$

5. The focal length of a convex mirror is 20 cm, its radius of the curvature will be

(a)

10 cm

(b)

20 cm

(c)

30 cm

(d)

40 cm

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

(a)

4125 $\mathring { A }$

(b)

3750$\mathring { A }$

(c)

6000$\mathring { A }$

(d)

2062.5$\mathring { A }$

7. The new wave mechanics of particles is called _______ mechanics.

(a)

quantum

(b)

statistical

(c)

classical

(d)

non-linear

8. The saturation current is proportional to the ________ of the radiation.

(a)

intensity

(b)

time of travel

(c)

target material

(d)

frequency

9. ______ theory explains photo electric effect.

(a)

Electromagnetic

(b)

Quantum

(c)

Wave

(d)

Corpuscular

10. Einstein's photoelectric equation is an equation of a _______

(a)

circle

(b)

sphere

(c)

straight line

(d)

ellipse

11. The ratio of the wavelengths for the transition from n=2 to n=1 in Li++, He+ and H is

(a)

1:2:3

(b)

1:4:9

(c)

3:2:1

(d)

4:9:36

12. 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

(a)

A and B have the same decay rate initially

(b)

A and B decay at the same rate always

(c)

B will decay at faster rate than A

(d)

A will decay at faster rate than B.

13. The ground state energy of hydrogen atom is 13.6 eV. The energy needed to ionize H2 atom from its second excited state.

(a)

1.51 eV

(b)

3.4 eV

(c)

13.6 eV

(d)

none

14. If γ is the frequency of characteristic X-ray line emitted by a target element of atomic number Z, then Moseley's law is

(a)

γ α Z

(b)

γ α $\sqrt Z$

(c)

γ α Z2

(d)

γ α Z3

15. The specific characteristic of a common emitter amplifier is

(a)

High input resistance

(b)

Low power gain

(c)

Signal phase reversal

(d)

Low current gain

16. The behaviour of Ge as semi-conductor is due to width of:

(a)

conduction band being large

(b)

forbidden band being small

(c)

conduction band being small

(d)

forbidden band being small and narrow

17. The frequency of output signal of LC oscillator circuit is 100 Hz with capacitance value 0.1μF. IF value of capacitance is taken as 0.2 μF, the frequency of output signal ______________

(a)

decreases by $\frac{1}{\sqrt2}$

(b)

increases by $\frac{1}{\sqrt2}$

(c)

decreases by $\frac12$

(d)

increases by $\frac12$

18. Semi-conductor has phosphorous as impurity then it will have ________

(a)

ne > > nh

(b)

ne < < nh

(c)

ne = nh

(d)

ne = nh = ni.

19. A NPN transistor conducts when

(a)

both collector and emitter are positive with respect to the base

(b)

collector is +ve and emitter is -ve with respect to the base

(c)

collector is +ve and emitter is same potential with respect to the base

(d)

both collector and emitter are -ve to the base

20. In an insulator the energy gap between the conduction band and valence band is of the order of

(a)

2MeV

(b)

5eV

(c)

1eV

(d)

10-3eV

21. The variation of frequency of carrier wave with respect to the amplitude of the modulating signal is called _______.

(a)

Amplitude modulation

(b)

Frequency modulation

(c)

Phase modulation

(d)

Pulse width modulation

22. In a video signal for transmission of picture what value of bandwidth is used in communication system?

(a)

2.4 MHz

(b)

4:2 MHz

(c)

24MHz

(d)

42 MHz

23. In television, blanking pulse is applied to

(a)

horizontal plates

(b)

vertical plates

(c)

control grid

(d)

filament

24. The materials used in Robotics are

(a)

Aluminium and silver

(b)

Silver and gold

(c)

Copper and gold

(d)

Steel and aluminum

25. A single strand of DNA, the building block of all living things, is about _________ nanometers wide.

(a)

Two

(b)

Three

(c)

Four

(d)

Five