DATE :- 01.01.24
CLASS - XII
SYED SIR CLASSES
PHYSICS
MCQ DPP_1
1. The Huygens’s concept of the secondary wave,
(a) Will allow us to find the focal length of a thick lens
(b) A geometrical way in order to calculate a wave front.
(c) Has been used to find out the velocity of light
(d) Has been used to describe polarization
2. Diffraction and interference indicate
(a) Wave nature
(b) particle nature
(c) Both (a) and (b)
(d) none of the above Interference of light waves:
3. The intensity at the site of the central maximum is I in an interference pattern created by two
identical slits. The intensity at the equivalent spot when either of the two slits has been closed
will be I0. Therefore we can write that,
(a) I = I0
(b) I = 2 I0
(c) I = 4 I0 (d) I and I0 will not be related to each other
4. It has been mentioned that two waves are having identical wavelength and amplitude
interfere in order to provide a minimum if the phase difference will be,
𝜋
3𝜋
(a) 0
(b) 2
(c) π
(d) 2
5. The first minimum on either side of the central maximum will be happening in a double slit
experiment where the path difference between the two paths will be
𝜆
𝜆
(a) 4
(b) 2
(c) 𝜆
(d) 2 𝜆
6. Two waves has been found to be originating from sources S1 and S2. This will be having zero
phase difference and the common wavelength λ will represent the destructive interference at
a point P completely when (S1 P - S2 P ) is
3
11
(a) 5 𝜆
(b) 4 𝜆
(c) 2 𝜆
(d) 4 𝜆
7. It has been mentioned that two waves are having the intensities in a ratio of 9 :1 in order to
create interference. The ratio between the maximum to minimum intensity can be written as,
(a) 10 : 8
(b) 9 :1
(c) 4 :1
(d) 2 :1
8. Two coherent monochromatic light beams having the intensities I and 4I have been
superposed. What will be the maximum and minimum possible intensities in the resultant
beam?
(a) 5I and I
(b) 5I and 3I
(c) 9I and I
(d) 9I and 3I
9. The displacement of an interfering light waves has been given as,
Y2 = 3sin ωt And,
𝜋
Y3 = 3 sin (ωt + 2 )
What will be the amplitude of resultant wave?
(a) 5
(b) 7
(c) 1
(d) zero
10. If light wave suffers reflection at the interface between air and glass, the change of phase of
the reflected wave is equal to
𝜋
(a) Zero
(b) 2
(c) π
(d) 2 π
11. When the slit separation is made three folds, the fringe width in a Young’s double slit
interference experiment will become,
1
3
(a) 3 fold
(b) 3
(c) 6 fold
(d) 6 fold
DATE :- 01.01.24
CLASS - XII
12. Two slits have been separated by a distance of 1mm. They are illuminated with the red light
of wavelength 6.5 × 10-7m. The interference fringes have been observed on a screen which
was kept 1m from the slits. The distance between the fifth bright fringe and the third dark
fringe will be?
(a) 0.65mm
(b) 1.63mm
(c) 3.25mm
(d) 4.88mm
13. The fringes of identical width has been observed if lights of wavelengths in the ratio 1: 2
have been used in the two separate set-ups of the Young’s double slit experiment. When the
ratio between the separation of the slit in the two cases has been mentioned as 2 :1 , find the
ratio of the distances between the plane of the slits and the screen in both of these set ups?
(a) 4 :1
(b) 1:1
(c) 1: 4
(d) 2 :1
14. A semiconductor is formed by
(a) covalent bond
(b) electrovalent bond
(c) co-ordinate bond (b) none of these
15. When a pure semiconductor is heated, its resistance
(a) goes up
(b) goes down
(c) remains same
(d) None of these
16. The strength of a semiconductor crystal comes from
(a) force between nuclei
(b) force between protons
(c) electron pair bond
(d) none of these
17. Identify the wrong statement.
(a) Inconductors, the valenceand conduction bandsoverlap.
(b) Substances with energy gap of the order of 10eV are insulators.
(c) The resistivity of semiconductors is lower than metals.
(d) The conductivity of metals is high.
18. When boron is added to silicon semiconductor, then the resulting material is
(a) conductor
(b) n-type semiconductor
(c) p-type semiconductor
(d) insulator
19. In n-type semiconductor, electrons are majority charge carriers but it does not show any
negative charge. The reason is
(a) mobility of electrons is extremely small
(b) electrons are stationary
(c) atom is electrically neutral
(d) electrons neutralize with
20. The conductivity of a semiconductor increases with increase in temperature because
(a) number density of free current carriers increases.
(b) relaxation time increases.
(c) both number density of carriers and relaxation time increase.
(d) number density of current carriers increases, relaxation time decreases but effect of
decrease in relaxation time is much less than increase in number density.
21. A forward biased p − n junction diode has a resistance of the order of
(a) 1Ω
(b) 1kΩ
(c) 1MΩ
(d) none of these
22. The depletion layer in the 𝑝 − 𝑛 junction region is caused by
(a) drift of holes
(b) diffusion of charge carriers
(c) migration of impurity ions
(d) drift of electrons
23. The barrier potential of a p-n junction depends on
(1) Type of semiconductor material
(2) amount of doping
(3) temperature
Which one of the following is correct?
(a) (1) and (2) only
(b) (2) only (c) (2) and (3) only (d) (1), (2) and (3)
24. In an unbiased 𝑝 − 𝑛 junction, holes diffuse from the p-region to n-region because of
(a) The attraction of free electrons of n-region.
(b) The higher hole concentration in p-region than that in n-region.
(c) The higher concentration of electrons in the n-region than that in the p-region.
(d) The potential difference across the 𝑝 − 𝑛 junction.
DATE :- 01.01.24
CLASS - XII
25. The leakage current across a p-n junction is due to
(a) minority carriers (b) majority carriers (c) junction capacitance (d) none of these
26. A p-n junction acts as a
(a) Controlled switch
(c) Unidirectional switch
(b) bidirectional switch
(d) none of these
27. In figure, 𝑉0 is the potential barrier across a 𝑝 − 𝑛 junction, when no battery is connected
across the junction.
(a) 1 and 3 both correspond to forward bias of junction
(b) 3 corresponds to forward bias of junction and 1 corresponds
to reverse bias of junction
(c) 1 corresponds to forward bias and 3 corresponds to
reverse bias of junction.
(d) 3 and 1 both correspond to reverse bias of junction.
Direction : In the following questions, a statement of assertion is followed by a
statement of reason. Mark the correct choice as:
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If assertion is false but reason is true.
(e) If both assertion and reason are false.
28. Assertion : p-n junction diode can be used even at ultra-high frequencies.
Reason : Capacitative reactance of a 𝑝 − 𝑛 junction diode increases as frequency increases.
29. Assertion : The conductivity of a semiconductor increases with rise of temperature.
Reason : On rising temperature covalent bonds of semiconductor breaks.
30. Assertion : An n-type semiconductor has a large number of electrons but still it is electrically
neutral.
Reason : An n-type semiconductor is obtained by doping an intrinsic semiconductor with a
pentavalent impurity.