Electromagnetic Waves
1. A magnetic field can be
produced only
(a) a
moving charge only (b) a changing electric field only
(c) both
of them (d) none of them
*2. Choose
the correct statement (s) :
The displacement current exists in the gap between
the plates of a capacitor when the charge on the capacitor
(a) is
increasing with time (b) is decreasing with time
(c) becomes
constant (d) is zero
3. Electromagnetic waves are
produced by :
(a) a
static charge (b) a uniformly moving charge
(c) an
accelerated charge (d) neutral particles.
*4. Which of
the following has/have zero average value in plane electromagnetic wave?
(a) electric
field (b) magnetic field
(c) electric
energy (d) magnetic energy
5. In a plane electromagnetic
wave the phase difference between electric and magnetic field vectors is :
(a) zero (b) p/4 (c) p/2 (d) p
6. An electromagnetic wave is
passing through a small volume of space. The energy in the volume oscillates
with
(a) the
frequency of the wave (b) double the frequency of the wave
(c) half
the frequency of the wave (d) zero frequency
7. Point out the wrong
statement : Electromagnetic waves
(a) are
transverse (b) are produced by accelerating charges
(c) electric
energy (d) magnetic energy
8. The dimensions of 1/m0e0 are :
(a) LT-1 (b) L-1T (c) L-2T2 (d) L2T-2
9. The ratio of the amplitudes
of electric and magnetic fields in an electromagnetic waves is
(a) Öm0e0 (b) 1Öm0e0 (c) m0e0 (d) 1/m0e0
10. The
amplitude of electric field in an electromagnetic waves is 5m-1. The
amplitude of the magnetic field is :
(a) 5T (b) 1.67 × 10-8 T (c) 1.5
× 109 T (d) 1.67 × 10-10 T
11. A plane
electromagnetic wave incident on a surface delivers momentum p and energy E.
Then :
(a) p
¹ 0, E ¹
0 (b) p = 0, E = 0 (c) p ¹
0, E = 0 (d) p = 0, E ¹
0
12. Select
the correct statement :
(a) Blue light has a higher momentum than red light
(b) Red
light has a higher momentum than blue light
(c) Red
light has an higher energy than blue light.
(d) Blue
light and red light have equal energies.
13. Heat
radiations are :
(a) g-rays (b) microwaves
(c) infrared
radiations (d) radiowaves.
14. Chose
the highest frequency waves :
(a) ground
waves (b) sky waves
(c) television
waves (d) visible light waves
15. Chose
the electromagnetic radiation relevant to telecommunication :
(a) ultraviolet (b) infrared (c) visible (d) microwave.
ANSWER SHEET
1.
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(c)
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2.
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(a) (b)
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3.
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(c)
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4.
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(a) (b)
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5.
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(a)
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6.
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(b)
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7.
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(c)
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8.
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(d)
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9.
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(b)
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10.
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(b)
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11.
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(a)
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12.
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(a)
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13.
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(c)
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14.
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(d)
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15.
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(d)
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OPTICS
Q.1 An object is placed unsymmetrically between two plane mirrors
such that a ray shooting form it is deviated through 144° on successive reflections from the two
mirrors. The total number of images seen in the two mirrors is
(a) 5 (b) 4 (c) 2 (d) infinite
Q.2 A ray of light incident normally on face AB of an isosceles
prism travels as shown in Fig. The least value of the refractive index the
prism must be
(a) Ö2 (b) 1.5 (c) Ö3 (d) 2.0
Q.3 Light rays following at angle of incidence A ¾ on prism of
angle A = 60°, image with minimum
divination given by
(a) 90° (b) 60° (c) 45° (d) 30°
Q.4 Angle of prism is A and its one surface is silvered. Light rays
falling at an angle of incidence 2A on the first surface returns back through the same path after
suffering reflection at the second silvered surface. The refractive index of
material of prism is
(a) 2 sin A (b) 2 cos A (c) ½ cos A (d) tan A
Q.5 An angle of minimum deviation for a prism of refractive index
1.5 is equal to the angle of the prism. The angle of the prism is
(a) 62° (b) 41° (c) 82° (d) 31°
Q.6 When a beam of light is allowed to fall normally on
the longer side of an isosceles right angled prism with refractive index
greater than Ö2 , it emerges fro m the prism after having suffered a
deviation. The angle of the deviation is
(a) 180° (b) > 90° but < 180°
(c) 90° (d) 60°
Q.7 There is a prism with refractive index Ö2 and the refracting angle equal to 30°. One of the refracting surfaces of the prism
is polished. A beam of monochromatic light will retrace its path if its angle
of incidence over the refracting surface of the prism is
(a) 0° (b) 30° (c) 45° (d) 60°
Q.8 A thin prism P1 with angle 4° and made from glass of refractive index 1.54
is combined with another thin prism P2 made from glass of refractive
index 1.72 to produce dispersion without deviation. The angle of the prism P2
is
(a) 5.33° (b) 4° (c) 3° (d) 2.6°
Q.9 The power of a lens (n = 1.25) is 3D. When immersed in a liquid
its power is -2D. The refractive index of the liquid is
(a) 1.3 (b) 1.4 (c) 1.5 (d) 1.6
Q.10 A convex lens of focal length ¦ is cut into two indentical
halves by a plane passing through a diameter and the two pieces are placed
symmetrically about the central axis with a small gap. A point source of light
is placed on the central line at a distance d such that d > ¦. The two pieces will give rise to
(a) no image (b) a single image of smaller intensity
(c) two real images (d) two virtual images
Q.11 The refractive index for flint glass for F line is 1.63327, for C
line is 1.61611 and for D line is 1.62100. The dispersive power of the flint
glass between F and C lines is
(a) 0.02764 (b) 0.2764 (c) 2.764 (d) 27.64
Q.12 The focal lengths of a thin convex lens are 100 cm and 96.8 cm
for red and blue rays respectively. Calculate the dispersive power of the
material of lens
(a) 0.968 (b) 0.032 (c) 9.68 (d) 6.30
Q.13 For making a direct vision spectroscope two prisms of crown glass
each of angle 4° and one prism of flint
glass are used, If refractive indices of crown and flint glasses for yellow
light are 1.515 and 1.655 respectively, the angle of flint glass prism is
(a) 3.2° (b) 6.3° (c) 3.6° (d) 7.2°
Q.14 An astronomical telescope has an angular magnification of
magnitude 5 for distant objects. The separation between the objective and the
eye-piece is 36 cm and the final image is formed at infinity. The focal length ¦e of the eye-piece are
(a) ¦0 = 45 cm, ¦e = - 9 cm (b) ¦0 = 50 cm, ¦e = 10 cm
(c) ¦0 = 7.2 cm, ¦e = 5 cm (c) ¦0 = 30 cm, ¦e = 6 cm
Q.15 An achromatic combination is to be obtained using a convex and a
concave lens. The two lenses chosen should have
(a)
their powers equal
(b)
their refractive indicates equal
(c) their dispersive powers equal
(d) the product of their powers and
dispersive powers equal
Q.16 In an electromagnetic field, the amplitude of magnetic field is 3 ´10-10T. If the frequency of wave
is 1012 Hz, the amplitude of
the associated em wave is
(a) 9´10-2 V/m (b) 3´10-10 V/m (c) 3´10-2 V/m (d) 1´10-18 V/m
Q.17 The optical path for l = 5890 A° is the same it goes through 1.00cm of perspex
or 1.14 cm of water. If the refractive index of water is 4/3 the refractive
index of perspex is
(a) 1.52 (b) 0.855 (c) 1.17 (d) 1.33
Q.18 The width of one of the two slits in a young’s double slit
experiment is double of the other slit. Assuming that the amplitude of the
light coming from a slit is proportional to the slit width, the ratio of the
maximum to the minimum intensity in the interfering pattern is
(a) 3 (b) 9 (c) 4 (d) 2
Q.19 Two coherent monochromatic light beams of intensities
I and 4I are superposed. The maximum
and minimum possible intensities in the resulting beam are
(a) 5I and I (b) 5I
and 3I (c) 9I and I (d) 9I
and 3I
Q.20 In the Young’s double slit experiment, the separation between the
slit is halved and the distance between the slit and screen is doubled. The
fringe width is
(a) unchanged (b) halved (c) doubled (d) quadrupled
Q.21 In Young’s double slit experiment, if the slit width are in the
ratio 1:9, the ratio of the intensity at minima to that at maxima will be
(a) 1 (b) 1/9 (c) 1/4 (d) 1/3
Q.22 The slits in a Young’s double slit experiment have equal width and
a monochromatic source is placed symmetrically with respect to the slits. The
intensity at the zero order (central) fringe is I0. If one of the slits is closed, the intensity at this
point will be
(a) I0 (b) I0/4
(c) I0/2 (d) 4I0
Q.23 If
Young’s double slit experiments is performed under water, then
(a) the
fringe width decreases (b) the fringe width increases
(c) the
fringe width remains unchanged (d) the fringes disappear
Q.24 A thin mica sheet is placed in front of Young’s double slit so
that both slits are cover
(a) the fringe width
decreases (b) the fringe width increase
(c) the fringe width
remains unchanged (d) the fringe system get displacement
Q.25 In the Young’s double slit experiment, the interference pattern is
found to have an intensity ratio between bright and dark fringes as 9. This
implies that
(a) the
intensities at the screen due to the two slits are 5 units and 4 units
respectively
(b) the
intensities at the screen due to two slits are 4 units and 1 unit respectively
(c)
the amplitude ratio is 3 (d) the amplitude ratio is 2
Q.26 In Young’s double slit experiment a thin transparent sheet (n = 1.55) is placed directly behind one
of the slits. The thickness of the sheet is such that the optical path length
of the light in the mica is 0.500lm where lm is the wavelength of light in the sheet.
The light used is 632.8nm. Then
(a) the
interference pattern is shifted by l/2
(b) the
thickness of mica is 204nm
(c) the dark fringe becomes
bright and vice versa
(d) the
interference pattern disappears
Q.27 In Young’s double slit experiment 52 fringes are obtained in the
field of view with sodium light of l = 5893 A°. The number of fringes in the same field of
view with mercury green light l=5461A° is
(a) 52 (b) 56 (c) 48 (d) 26
Q.28 A thin film (n = 1.33)
seen by light of wavelength 532nm appears dark by normal reflection. Its
thickness is
(a) 200nm
(b) 100nm (c) 400nm (d) 266nm
Q.29 White light falls normally upon a film of soapy
water (n = 1.33) whose thickness is 5
´10-5cm. If seen in reflected
light, it appears.
(a) white
(b) dark (c) green (d) red
Q.30 Light of wavelength 4500A° is found to be missing in
the reflected light in a thin air film interference experiment viewed normally.
Thickness of the film is 6.75´10-7m, then light
of wavelength
(a) 5400A° will also be missing in reflecting
light
(b) 6750A° will show a maximum in reflected light
(C) 5400A° will be missing in the transmitted light
(d) 5400
A° will show a maximum in the reflected light
Q.31 A diffraction pattern is formed on a screen using red light. What
happens if red light is reflected by green light?
(a) no
change
(b) the
central maximum becomes narrower and intense
(c) the
central maximum becomes broader and less intense
(d) the
central maximum becomes narrower and more intense
Q.32 A beam of light of wavelength 600nm from a distant source falls on
a single slit 1.00mm wide and the resulting diffraction pattern is observed on
a screen 2m away. The distance between the first dark fringe on either side of
the central bright fringe is
(a) 1.2
cm (b) 1.2 mm (c) 2.4cm (d) 2.4 mm
ANSWER
OPTICS
1.
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(a)
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2.
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(a)
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3.
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(d)
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4.
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(b)
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5.
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(c)
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6.
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(a)
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7.
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(c)
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8.
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(c)
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9.
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(c)
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10.
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(c)
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11.
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(a)
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12.
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(b)
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13.
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(b)
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14.
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(d)
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15.
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(d)
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16.
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(a)
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17.
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(a)
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18.
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(b)
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19.
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(c)
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20.
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(d)
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21.
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(c)
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22.
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(b)
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23.
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(a)
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24.
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(c)
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25.
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(b,d)
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26.
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(abc)
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27.
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(b)
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28.
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(a)
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29.
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(c)
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30.
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(d)
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31.
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(d)
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32.
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(d)
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Modern
Physics
Q.1 For a slow moving electron, having kinetic energy E, the deBroglie wavelength is proportional to
(a) E1/2 (b) E (c) E-1/2 (d) E-2
Q.2 A photon of frequency v has a momentum associated with it. If c is the velocity of light, this
momentum is
(a) hv/c2 (b) hv/c (c) v/c (d) h/c
Q.3 The momentum of a photon and an electron are equal, then
(a) both
have equal energy (b) electron has more energy
(c) photon
has more energy (d) photon has no energy
Q.4 The threshed wavelength for
photoelectric emission from a material is 5200A°. Photoelectrons will be
emitted when the material is illuminated with monochromatic radiation from
(a) 50
watt infrared lamp (b) 1 watt infrared lamp
(c) 50
watt ultraviolet (d) 1 watt ultraviolet lamp
Q.5 A source of monochromatic light is placed at a
distance of 1m from a photocell and cut off potential is found to be V0. If the distance is
doubled, The cut off potential will be
(a) 2V0 (b) 1.5V0 (c) V0 (d) 0.5V0
Q.6 A photocell is illuminated by a small bright source placed one metre
away. When the same source is placed two metre
away, the electrons emitted by the photo cathode
(a) each
carries one quarter of its previous energy
(b) each
carries one quarter of its previous momenta
(c) are
half as numerous
(d) are
one quarter as numerous
Q.7 In hydrogen spectrum Ha line arises due to
transition of electron from n = 3 to n = 2. In the spectrum of singly ionized
helium there is a line having almost the same wavelength as that of Ha line. This is due to the transition of
electron between the states.
(a) 3 ® 2 (b) 4 ® 2 (c) 5 ® 3 (d) 6 ® 4
Q.8 Atomic hydrogen is excited to the nth energy level. The maximum number of
spectral lines which it can emit while returning to the ground state is
(a) ½ n (n-1) (b) ½
n (n+1) (c) n
(n-1) (d) n
(n+1)
Q.9 The X-rays beam coming from an X-rays tube will be
(a) monochromatic
(b) having all wavelength smaller than a certain maximum
wavelength
(c) having all wavelength larger than a certain minimum
wavelength
(d) having all wavelength lying between a minimum and a
maximum wavelength
Q.10 The
wavelength l of the X-rays line Ka of an anticathode element
of atomic number Z is nearly proportional to
(a) Z2 (b) (Z-1)2 (c) 1/Z-1 (d) 1/ (Z-1)2
Q.11 The wavelength of Ka line from an element of
atomic number 41 is l1 then the wavelength of Ka line of an element of
atomic number 21 is
(a) 4l (b) l/4 (c) 3.08l (d) 0.26l
Q.12 The radius of a nucleus is
(a) proportional
to its mass number
(b) inversely
proportional to its mass number
(c) proportional
to the cube root of its mass number
(d) not
related to its mass number
Q.13 The approximate density of nuclear matter is
(a) 105kg/m3
(b) 1010kg/m3 (c) 1015kg/m3 (d) 1020kg/m3
Q.14 The a-, b- and g- rays emitted by a
radioactive substance are passed through a region containing a magnetic field
at right angles to their path. Then
(a) energy
gained by a-rays will be maximum
(b) energy
gained will be zero by all the three rays
(c) momentum
of rays will not change, while those a-and b-rays
(d) momentum
change will be zero for all the three days
Q.15 The number of alpha particles emitted per minute by
a small amount of substance was 480 initially and 240 after 2 hours. After
another 4 hours the expected rate of emission per minute is
(a) 0 (b) 60 (c) 80 (d) 120
Q.16 Consider a radioactive material of half-life 10
minutes. If one of the nuclei decays now, the next one will decay
(a) after
1 minute (b) after 1 In 2 minute
(c) after
1/N minutes, where N is the number of
nuclei present at that moment
(d) after
any time
Q.17 A radioactive material has half lives of 1620 years
and 405 years for a and b emission respectively. The material decays
by simultaneous a and b emission. The time in which one-fouth of the
material remains intact is
(a) 4675
years (b) 720 years
(c) 648
years (d) 324 years
Q.18 The kinetic energy of a 300K thermal neutron is
approximately
(a) 300eV
(b) 300keV (c) 0.025eV (d) 1.1MeV
Q.19 Assuming that 200 MeV of energy is released per
fission of 92235U nuclei, then the mass of 82235U
consumed per day in a fission reactor of power 1 megawatt will apprxoimately be
(a) 10-2g (b) 1g
(c) 100g
(d) 1000g
Q.20 The equation 411H®24He + 2e + 2v + 26 MeV
represents.
(a) b-decay (b) g-decay (c) fusion (d) fission
Q.21 The binding energy of deutron 21H
is 1.112 MeV per nucleon and a-particle 42He has a binding energy of 7.0471
MeV per nucleon. Then in the relation
21H + 21H®42He+ Q
the energy Q released is
(a) 1MeV (b) 11.9MeV
(c) 23.8MeV (d) 9.31MeV
Q.22 With p for
photon and n for neutron, the nuclear
forces have strengths in the order of
(a) p – p > p – p > n – n (b) n
– n > p – n > p – p
(c) n – n > p – p > p – n (d) n – n = p
– p = p – n
Q.23 The minimum energy of a g-rays photons for pair production is nearly
(a) 1.1eV
(b) 1.1keV (c) 1.1MeV (d) 1.1BeV
Q.24 When do two protons attracts each other
(a) the
distance between them is 10-10m
(b) the
distance between them is 10-1m
(c) the distance between them is 10-15m
(d) this will never happen.
Q.25 A proton and an electron are accelerated by
same potential difference have de-Broglie wavelength lp and le.
(a) le
= lp (b) le
< lp (c) le
> lp
(d) none of these.
Q.26 An
electron with initial kinetic energy of 100 eV is acceleration through a
potential difference of 50 V. Now the de-Broglie wavelength of electron becomes
(a) 1 Å (b) Ö1.5 Å (c) Ö3 Å (d) 12.27 Å.
Q.27 Which of the following is
correct?
(a)
Photoelectric current is proportional to applied voltage.
(b)
Increase in frequency of incident radiations results in the increase in
the photocurrent.
(c)
Increases in applied voltage results in the increase in the
photocurrent.
(d)
Increase in intensity of incident light results in the increase in
photocurrent.
Q.28 An electron microscope uses
electrons accelerated by a voltage of 50 kV. The de-Broglie wavelength
associated with the electrons is
(a) 5.5 ´ 10-10 m (b) 5.5 ´
10-11 m (c) 5.5 ´
10-12 m (d) 5.5 ´
10-14 m
Q.29 If de-Broglie wavelength
associated with a neutron is 1.4 Å then K.E. of the neutron is (given mn =
1.675 ´ 10-27 kg)
(a) 0.01 3
eV (b) 0.049 eV (c) 0.93 eV (d) 0.042 eV
Q.30 Light of wavelength 4000 Å
is incident on barium. Photo electrons emitted describe a circle of radius 50
cm by a magnetic field of flux density 5.26 ´
10-6 Tesla. Work function of the barium is
(a) 3200 Å (b) 3400 Å
(c) 3600 Å (d) 3800 Å
Q.31 If h is Planck is constant,
m is mass of electron and C is velocity of light, then the dimension of h/mc
is
(a) [M0L0T] (b) [M0L0T0] (c) [M0LT0] (d) [ML0T0]
ANSWERSHEET
1.
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(d)
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2.
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(c)
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3.
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(c)
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4.
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(c),(d)
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5.
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(c)
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6.
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(d)
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7.
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(d)
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8.
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(c)
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9.
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(c)
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10.
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(d)
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11.
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(a)
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12.
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(c)
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13.
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(c)
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14.
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(b)
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15.
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(b)
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16.
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(d)
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17.
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(c)
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18.
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(c)
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19.
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(b)
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20.
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(c)
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21.
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(c)
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22.
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(d)
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23.
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(c)
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24.
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(c)
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25.
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(c)
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26.
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(a)
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27.
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(d)
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28.
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(c)
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29.
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(d)
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30.
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(c)
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31.
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(b)
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Semiconductor
Q.1 The output of amplifier-1 is
the input for amplifier –2. If their gains
are A1 and A2 respectively, the total
gain of this two-stage amplifier is
(a) A1 + A2 (b) A1 - A2 (c) A1
´ A2 (d) A1 / A2
Q.2 When donors are added to a
semi-conducting material
(a) number of electrons increases, number of holes remains unaltered
(b) number of electrons increases, number of holes decreases
(c) number of electrons decreases, number of holes increases
(d) number of electrons remains unaltered, number of holes
decreases
Q.3 A piece of copper and
another of germanium are cooled from room temperature to 80K. The resistance of
(a) each of them increases
(b) each of them decreases
(c) copper increases and germanium decreases
(d) copper decreases and germanium increases
Q.4 The impurity atoms with
which pure silicon should be doped to make a P-type semi-conductor are those of
(a) phosphors (b) antimony (c) boron (d) aluminum
Q.5 The concentration densities of
electrons and holes in a N-type
semi-conductor are n and p respectively. If this semi-conductor
is heated from temperature T to T’, then
(a) p increases and n decreases (b) n
increases and p decreases
(c) both n and p increase, but always n>>p (d) both n and p increase, but n » p» nI (T)
Q.6 Read the following
statements carefully :
Y : The resistivity of a semi-conductor decreases
with increase of temperature
Z : In a conducting solid, the rate of collision
between free electrons and ions increases with increase of temperature
(a) Y is true but Z is false (b) Y
is false but Z is true
(c) Both Y and Z are true (d) Y
is true and Z is the correct reason
for Y
Q.7 The depletion layer in a PN junction contains charges that are
(a) Mostly majority carries (b) Mostly minority carries
(c) Mobile
donor and acceptor ions (d) Fixed donor and acceptor ions
Q.8 When a forward bias is
applied to a junction diode
(a)
Potential barrier increases
(b)
Potential barrier decreases
(c) Majority-
carrier current decreases to zero
(d) Minority-carries current decreases to zero
Q.9 The width of the depletion
layer of a junction
(a) decreases
with light doping (b) increase with heavy doping
(c) is independent of applied voltage (d) is increased under reverse bias
Q.10 The turn-on voltage of a Ge junction diode is nearly
(a) 0.7 V (b) 0.3V (c) 1.0V (d) 0.1V
Q.11 In an unbiased PN-junction, the junction current at
equilibrium is
(a) due to diffusion of minority carries only
(b) ue to diffusion of majority carries only
(c) zero, because equal but opposite carries are crossing the
junction
(d) zero, because no charges are crossing the junction
Q.12 A full wave rectifier is
being used to rectify an alternative voltage of frequency 50Hz. The number of
pulses of rectified current obtained in one second is
(a) 25 (b) 50 (c) 100 (d) 200
Q.13 for transistor action
(a) the collector must be more heavily doped than the emitter
(b) the collector-base region must be reversed biased
(c) the
base region must be wide
(d) the emitter must be N-type
material
Q.14 A transistor connected in CB configuration has
(a) a low input resistance and a high output resistance
(b) a high input resistance and a low output resistance
(c) a low input resistance and a low output resistance
(d) a high input resistance and a high output resistance.
Q.15 When the emitter current of
a transistor is charged by 1mA, its collector current changes by 0.995mA. Then
(a)
Common base gain a = 0.995
(b)
Common emitter gainb = 199
(c) Base current IB
= 0.005mA
(d) Reverse
leakage currents ICEO and ICBO are related as ICEO = 200 ICBO
Q.16 In an NPN transistor circuit, the collector current is 10mA. If 90% of
the electors emitted reach the collector
(a) the emitter current will be 9mA (b) the emitter current will be 11mA.
(c) the base current will be 1mA. (d) the base current will be-1mA.
Q.17 The condition which must be
satisfied to operate the transistor in saturation mode is
(a) the E / B and C / B junctions are forward biased
(b) the E/B junction is forward biased and C/B
junction is reverse biased
(c) the E/B junction is reverse biased and C /B
junction is forward biased
(c)
the E /B and C /B junctions are reverse biased
Q.18 A transistor is used in common emitter mode as an amplifier.
Then
(a)
the base-emitter junction is forward biased
(b)
the base-emitter junction is reverse biased
(c)
the input signal is connected in series with the voltage applied to the
base-emitter junction
(d)
the input signal is connected in series with the voltage applied to bias
the base-collector junction.
Q.19 n the middle of the depletion layer of a reverse-biased p-n
junction, the
(a)
electric field is zero (b) potential is maximum
(b)
electric field is maximum (d) potential is zero
Q.20 For a transistor amplifier, the voltage gain
(a)
remains constant for all frequencies
(b)
is high at high and low frequencies and constant in the middle
frequency range
(c)
is low at high and low frequencies and constant at mid frequencies
(d)
none of the above
Q.21 When npn transistor is used as an amplifier
(a)
electrons move from base to collector
(b)
holes move from emitter to base
(c)
electrons more from collector to base
(d)
holes move from base to emitter.
Semiconductor Physics
1.
|
(c)
|
2.
|
(b)
|
3.
|
(d)
|
4.
|
(c), (d)
|
5.
|
(d)
|
6.
|
(c)
|
7.
|
(d)
|
8.
|
(b)
|
9.
|
(d)
|
10.
|
(b)
|
11.
|
(c)
|
12.
|
(c)
|
13.
|
(b)
|
14.
|
(a)
|
15.
|
(a), (b)
|
16.
|
(b), (c)
|
17.
|
(a)
|
18.
|
(a), (c)
|
19.
|
(a)
|
20.
|
(c)
|
21.
|
(a)
|
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