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Recent questions in Physics
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JEEMAIN and NEET
>>
Physics
Physics
Class11
Class12
Find the amplitude of the electric field in a parallel beam of light of intensity
2
W
/
m
2
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q67
medium
asked
Mar 1, 2014
by
thanvigandhi_1
1
answer
The electric field in an electromagnetic wave is given by
E
=
50
N
/
C
sin
ω
(
t
−
x
/
c
)
. Find the energy contained in a cylinder of cross-section
10
c
m
2
and length 50 cm along the x-axis.
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q66
medium
asked
Mar 1, 2014
by
thanvigandhi_1
1
answer
The average energy flux of sunlight is
1
k
W
/
m
2
. This energy is falling normally on the plate surface of area
10
c
m
2
which completely absorbs the energy. How much force is exerted on the plate if it is exposed to sunlight for 20 minutes?
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q65
medium
asked
Mar 1, 2014
by
thanvigandhi_1
1
answer
The magnetic field in a plane electromagnetic wave is given by
B
=
100
μ
T
sin
[
(
2
×
10
15
s
−
1
)
(
t
−
x
/
c
)
]
. Calculate the average energy density corresponding to the electric field.
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q64
medium
asked
Mar 1, 2014
by
thanvigandhi_1
1
answer
A light beam travelling in the x-direction is described by the electric field
E
y
=
300
V
/
m
sin
ω
(
t
–
x
/
c
)
. An electron is constrained to move along the y-direction with a speed of
2
×
10
7
m
/
s
. Find the maximum magnetic force on the electron
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q63
medium
asked
Mar 1, 2014
by
thanvigandhi_1
1
answer
A plane sinusoidal linearly polarized electromagnetic wave of wavelength
5
×
10
−
7
m
travels in vacuum in the direction of
x
- axis. The average intensity of the wave per unit area is
0.1
W
/
m
2
and the plane of vibration of electric field is parallel to
y
- axis. The equations describing the electric and magnetic field of this wave is
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
medium
asked
Mar 1, 2014
by
thanvigandhi_1
1
answer
A
60
W
monochromatic point source radiating equally in all directions in vacuum is being monitored at a distance of
2
m
. Determine the amplitude if the electric field.
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q61
medium
asked
Mar 1, 2014
by
thanvigandhi_1
1
answer
A laser emits a beam of light of
2
m
m
diameter. If the power of beam is
10
m
W
, the intensity of the beam of light is
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q60
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
We can establish an instantaneous displacement current of
1
A
in the space between the two plates of a
1
μ
F
parallel plate capacitor by varying voltage at the rate of
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
displacement-current
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
A parallel plate capacitor has circular plates, each of radius
5
c
m
. It is being charged so that electric field in the gap between its plates rises steadily at the rate of
10
12
V
/
m
s
. What is the displacement current?
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
displacement-current
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
A radio wave of intensity
I
is reflected by a surface. The intensity
(
I
)
, if pressure exerted on the surface is
2
×
10
−
8
N
/
m
2
, will be:
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
What is order of energy of X-rays
(
E
X
)
, radio waves
(
E
R
)
, and micro waves
(
E
M
)
?
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
electromagnetic-specturm
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
A TV tower has a height of
100
m
. The area covered by the TV broadcast, if radius of the earth is
6400
k
m
, will be:
jeemain
aipmt
physics
cbse
class12
ch15
communication-systems
bandwidth-of-signals-and-transmission-medium
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
Some radio waves of frequency of about
1.5
×
10
9
Hz were received by a radio-telescope from distant star. If the speed of the waves is
3
×
10
5
k
m
/
s
, then the wave- length of the wave will be:
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
electromagnetic-spectrum
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
An object is placed at some distance from a radio station. If the interval between transmission and reception of pulses is
2.66
×
10
−
2
s
e
c
, then the distance is:
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
electromagnetic-spectrum
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
The speed of light in air, if an electromagnetic wave is travelling in air whose dielectric constant is
k
=
1.006
, will be :
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q52
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
The energy of photon of electromagnetic radiation of wavelength =
2000
A
∘
is:
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
The AM radio wave bends appreciably round the corners of a
1
m
×
1
m
board but the FM wave only negligibly bands. If the average wavelength of the AM and FM waves are
λ
a
and
λ
f
, then
jeemain
aipmt
physics
cbse
class12
ch15
communication-systems
modulation
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
If an electromagnetic wave of frequency
v
=
3.0
M
H
z
passes from vacuum into a dielectric medium with permittivity
e
=
4.0
then
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
The displacement
y
of a particle in a medium can be expressed as
y
=
10
−
6
sin
(
100
t
+
20
x
+
π
4
)
m
, where
t
is in second and
x
is in metre. The speed of the wave is
jeemain
aipmt
physics
cbse
class11
ch15
waves
displacement-relation-in-a-progressive-wave
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
An uniform electric field and an uniform magnetic field are acting along the same direction in a certain region. If an electron is projected along the direction of the fields with a certain velocity, then
jeemain
aipmt
physics
cbse
class12
ch4
moving-charge-and-magnetism
motion-in-combined-electric-and-magentic-fields
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. The path of the particle will be a
jeemain
aipmt
physics
cbse
class12
ch4
moving-charge-and-magnetism
motion-in-combined-electric-and-magentic-fields
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
A wave travelling along the
x
- axis is described by the equation
y
(
x
,
t
)
=
0.005
cos
(
α
x
−
β
t
)
. If the wavelength and time period of the wave are
0.08
m
and
2
s
, respectively, then
α
and
β
in appropriate units are
jeemain
aipmt
physics
cbse
class11
ch15
waves
displacement-relation-in-a-progressive-wave
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
If a source of power
4
k
W
produce
10
20
photons/s, the radiation belongs to a part of spectrum called
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
electromagnetic-specturm
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
The time period of a charged simple pendulum in an electric field is:
jeemain
aipmt
physics
cbse
class12
ch1
electric-charges-and-fields
electric-field
medium
asked
Feb 28, 2014
by
thanvigandhi_1
1
answer
If activity of a radioactive substance's
A
1
at time
t
1
&
A
2
at time
t
2
(
>
t
1
)
. Its decay constant is
λ
. Then
jeemain
physics
class12
atoms-and-nuclei
easy
asked
Feb 28, 2014
by
yamini.v
1
answer
If ratio of molecular masses of two radioactive substances is
1
2
and ratio of decay constant is
5
3
. Then ratio of their initial activity per mole will be
jeemain
physics
class12
atoms-and-nuclei
easy
asked
Feb 28, 2014
by
yamini.v
1
answer
x atoms of a radioactive element emit y beta particles per second . Then the decay constant of element is (in
s
−
1
) .
jeemain
physics
class12
atoms-and-nuclei
easy
asked
Feb 28, 2014
by
yamini.v
1
answer
The equation :
4
1
1
H
→
4
2
H
e
2
+
+
2
e
−
+
32
M
e
V
represents
jeemain
physics
class12
atoms-and-nuclei
easy
asked
Feb 28, 2014
by
yamini.v
1
answer
Which of the following is correct statement ?
jeemain
physics
class12
atoms-and-nuclei
easy
asked
Feb 28, 2014
by
yamini.v
1
answer
22
N
e
Nucleus after absorbing energy , decays into two
α
−
particles and an unknown nucleus . The unknown nucleus is
jeemain
physics
class12
atoms-and-nuclei
easy
asked
Feb 28, 2014
by
yamini.v
1
answer
The half -life period of a radioactive element A is same as mean life of another radioactive element B . Initially both of them have same number of atoms
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 28, 2014
by
yamini.v
1
answer
A nucleus with mass number 200 initially at rest emits and
α
−
particle . If Q value of reaction is 4.2MeV .Then kinetic energy of
α
−
particle will be
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 28, 2014
by
yamini.v
1
answer
Two radioactive materials A & B have decay constants 12X & X respectively . If initially they have same no.of nuclei , then ratio of no. of nuclei of A to B will be
1
e
after a time
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 27, 2014
by
yamini.v
1
answer
Half life of a radioactive substance A is 4 days . The probability that a nucleus will decay in two half-lives is :
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 27, 2014
by
yamini.v
1
answer
If a star can convert all He nuclei completely into oxygen nuclei . The energy released per oxygen nuclei is . [Mass of nucleus He is 4.0026 amu & mass of oxygen nucleus is 15.9994]
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 27, 2014
by
yamini.v
1
answer
A star initially has
10
4
deuterons . It produces energy via the process
1
H
2
+
1
H
2
→
1
H
3
+
P
and
1
H
2
+
1
H
3
→
2
H
e
4
+
n
If average power radiated by star is
10
16
W
the deutron supply of star is exhausted in a time of order of
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 27, 2014
by
yamini.v
1
answer
The binding energy of two nuclei A & B are X & Y . Two atoms of A fuse to give one atom of B an energy P is released . Then
jeemain
physics
class12
atoms-and-nuclei
easy
asked
Feb 27, 2014
by
yamini.v
1
answer
The half life of radioactive radon is 3.8 days . The time , at end of which
1
20
t
h
of radon sample will remain undecayed is
jeemain
physics
class11
ch13
nuclei
nuclear-physics
radioactivity
half-life
easy
asked
Feb 27, 2014
by
yamini.v
1
answer
The displacement
y
of a wave travelling in the
x
- direction is
y
=
10
−
4
sin
(
600
t
–
2
x
+
π
3
)
m
, where,
x
is in
m
and
t
is in
s
. The speed of the wave motion in
m
/
s
is
jeemain
aipmt
physics
cbse
class11
ch15
waves
displacement-relation-in-a-progressive-wave
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
An electric line of force in the
x
y
plane is given by equation
x
2
+
y
2
=
1
. A particle with unit positive charge, initially at rest at the point
x
=
1
,
y
=
0
in the
x
y
plane
jeemain
aipmt
physics
cbse
class12
ch1
electric-charges-and-fields
electric-field
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
If
c
is the speed of electromagnetic waves in vacuum, their speed in a medium of dielectric constant
K
and relative permeability
μ
r
is
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q40
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
A beam of light travelling along
x
- axis is described by the electric field
E
y
=
(
600
V
/
m
)
sin
ω
(
t
−
x
/
c
)
then maximum magnetic force on a charge
q
=
2
e
, moving along
y
- axis with a speed of
3.0
×
10
7
m
/
s
is
(
e
=
1.6
×
10
−
19
C
)
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q39
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
About 5% of the power of a
100
W
light bulb is converted to visible radiation. What is the average intensity of visible radiation at a distance of
10
m
from the bulb?
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q38
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
A parallel plate capacitor of area
50
c
m
2
and plate separation
3
m
m
is charged initially to
80
μ
C
. Due to a radioactive source nearby, the medium between the plates gets slightly conducting and the plate loses charge initially at the rate of
1.5
×
10
−
8
C
/
s
. What is the magnitude and direction of displacement current?
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
displacement-current
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
A parallel plate capacitor with plate area
A
and separation
d
between the plates is charged by a constant current
i
. Consider a plane surface of area
A
/
4
parallel to the plates and drawn symmetrically between the plates. Calculate the displacement current through this area.
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
displacement-current
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
Find the energy of a photon in electron volt of microwaves having wavelength
3
m
m
.
(
1
e
V
=
1.6
×
10
−
19
J
)
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q35
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
Light with an energy flux of
18
W
/
c
m
2
surface has an area of
20
c
m
2
falls on a non-reflecting surface at normal incidence. If the , the average force exerted on the surface during a
30
minute time span is
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q34
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
The magnetic field in a plane electromagnetic wave is given by
B
y
=
2
×
10
−
7
sin
(
0.5
×
10
3
x
+
1.5
×
10
11
t
)
T
The wavelength and frequency of the wave are
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q33
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
A plane electromagnetic wave of frequency
25
M
H
z
travels in free space along the
x
- direction. At a particular point in space and time,
E
=
6.3
j
V
/
m
. What is B at this point?
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
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