A closed surface contains two equal and opposite charges. The net electric flux from the surface will be
1.negative
2.positive
3.zero
4.data is insufficient
A diffraction grating has 500 lines per mm. Its slit spacing or grating element will be equal to
1.500 mm
2.5 x 10-3 mm
3.2 x 10-5 mm
4.2 x 10-3 mm
A hollow metallic sphere of 8cm diameter is charged with 4 x 10 8C. The potential on its surface will be
1.900 volts
2.9000 volts
3.90 volts
4.zero
A light ray traveling form rarer to denser medium suffers a phase change of
1.60?
2.90?
3.180?
4.45?
A point source of light placed in a homogeneous medium gives rise to
1.a cylindrical wave front
2.an elliptical wave front
3.a spherical wave front
4.a plane wave front
A thing that emits its own light is
1.luminous
2.non-luminous
3.incandescent
4.bright
An electric charge at rest produces
1.only a magnetic field
2.only an electric field
3.neither electric field nor magnetic field
4.both electric and magnetic fields
An electric field can deflect
1.neutrons
2.?-rays
3.both glass rod and silk acquire negative charge
4.none
appearance of colour in thin films is due to
1.diffraction
2.dispersion
3.interference
4.polarization
Central spot of Newtons rings
1.bright
2.dark for large wavelength
3.dark
4.bright for large wavelength
Crystals of a material can behave as
1.Convex lens
2.Interferometer
3.Diffraction grating
4.Concave
Diffarction fringes are
1.equally spaced
2.distance between them increases
3.distance between then decreases
4.they are adjacent with no space in between
Diffraction effect is
1.more for a round edge
2.less for a round edge
3.more for a sharp edge
4.less for a sharp edge.
Electric charge of 100 ?C is 13cm apart from another charge 16.9?C electric force between them is
1.9x107N
2.900N
3.9x105N
4.9x106N
Electric flux linked with a surface will be maximum when
1.the surface is held parallel to the electric field
2.the surface is held perpendicular to the electric field
3.the surface makes an angle of 45?with the field
4.all of the above
Electric force between two point charges in air or vacuum is F. If we replace air or vacuum by an insulator (dielectric) of relative permitivity Cr the force between the charges will
1.decrease
2.increase
3.remain constant
4.depends upon composition of dielectric
Electric intensity being a vector quantity always points
1.along the direction of force experienced by a unit positive charge
2.opposite to the direction of force experienced by a unit positive charge
3.perpendicular to the direction of force experienced by a uit positive charge
4.any of above
gives the definition of metre in terms of wavelength of red cadmium light
1.Newton
2.Einstein
3.Michelson
4.Galileo
If free space between the plates of a capacitor is replaced by a dielectric
1.The potential difference remains constant capacittance and energy stored increases
2.The potential difference remains constant capacittance decreases and energy increases
3.The potential difference decreases but both capacitance and energy increase
4.both potential difference and capacitance decrease but energy increases
If the distance between the two point charges become half then force between them becomes
1.double
2.half
3.four times
4.remains same
In a plane polarized light
1.vibration in all direction
2.vibration in two mutually perpendicular directions
3.vibration take place in a direction perpendicular to the direction of propagation of light
4.no vibration at all
In an interference pattern
1.bright fringes are wider than dark fringes
2.dark fringes are wider than bright fringe
3.both dark and bright fringes are of equal width
4.central fringes are brighter than the outer fringes
In double slit experiment if one of the two slit is covered then
1.no interference fringes are observed
2.no diffraction fringes are observed
3.no fringes observed
4.interference pattern not disturbed
In Michelson interferometer to switch the fringe from bright to dark the mirror should be displaced through
1.? / 2
2.?/3
3.?/6
4.?/4
In monochromatic red light a blue book will probably appear to be
1.black
2.purple
3.green
4.no scientific reasoning available
In the shadow of a ball the central portion appears bright that happens due to
1.Interference
2.Diffraction
3.Polarization
4.Refraction
In Young double slit experiment, if white light is used
1.alternate dark and bright fringes will be seen
2.coloured fringes will be seen
3.no interference fringes will be seen
4.impossible to predict
In Youngs double slit experiment the fringe spacing is equal to
1.d?D
2.2?d/D
3.?D/d
4.?d/D
Light on passing through a Polaroid is
1.plane polarized
2.un-polarized
3.circularly polarized
4.elliptically polarized
The blue colour of the sky is due to
1.diffraction
2.reflection
3.polarization
4.scattering
The condition for constructive interference of two coherent beams is that the path difference should be
1.integral multiple of ?/2
2.integral multiple of ?
3.odd integral multiple of ?/2
4.even integral multiple of ?
The electric lines of force are
1.imaginary
2.physically existing every where
3.physically existing near the charges
4.depends upon case
The force per unit charge is know as
1.electric flux
2.electric intensity
3.electric potential
4.all of above are same
The locus of all points in a medium having the same phase of vibration is called
1.crest
2.trough
3.wavelength
4.wave front
The metallic spheres A and B of radii 2m and 4m respectively carry the same charge 4 x 10 8C. If the spheres are connected by a copper wire
1.charge will flow from A to B
2.charge will flow from B to A
3.no flow of charge will occur
4.both a and b are possible
The minimum charge on any object cannot be less than
1.1.6 x 10-19C
2.3.2 x 10-19C
3.9.1 x 109C
4.no definite value exist
The velocity of light was determined accurately by
1.Newton
2.Michelson
3.Huygen
4.Young
The wavelengthe of X-rays is of the order of
1.10A?
2.1000 A?
3.1A?
4.100 A?
Tick the correct statement
1.the electric lines of force have no physical existence
2.they expand laterally and contract longitudinally
3.they do not cross each other and group together in dielectric
4.all the above statements are true
Tick the only wrong statement.
1.similar charges repel each other
2.dissimilar charges attract each other
3.repulsion is the sure test of electrification
4.an electrically neutral body is repelled both positively and negatively charged bodies
Two charges are placed at a certain distance. If the magnitude of each charge is doubled the force will become
1.1/4th of its original value
2.1/8th of its original value
3.4 times of its original value
4.8 times of its original value
Two similar charges each of one coulomb placed in air one meter apart repel each other with a force
1.9 x 109N
2.9.2 x 104N
3.9 x 109N
4.9 x 107N
Two sources of light are coherent if they emit rays of
1.same wavelength
2.same amplitude of vibration
3.same wave length with constant phase difference
4.same amplitude and wavelength
Wavelength of X-rays falling at glancing angle of 30? on a crystal with atmic spacing 2 x 10-10 for the fist order diffraction is
1.4 x 10-10 m
2.2 x 10-10 m
3.0.02x10-10m
4.20x10-10m
When crest of one wave falls over the trough of the other wave this phenomenon is known as
1.polarization
2.constructive interference
3.destructive interference
4.diffraction
When one mirror of a Michelson Interferometer is moved a distance of 0.5 mm we observe 2000 fringes. What will be wavelength of light used?
1.5000 nm
2.5000A?
3.500m
4.2000um
When we rub a glass rod with a silk cloth then
1.glass rod acquires negative charge while silk acquires positive charge
2.glass rod acquires positive charge while silk acquires negative charges
3.both glass rod and silk acquire negative charge
4.both glass rod and silk acquire positive charge
Which experiment shows that wavelength of light is smaller than that of sound
1.Diffraction
2.Polarization
3.Interference
4.Reflection
Which one of the following cannot be polarized?
1.radio waves
2.ultraviolot rays
3.X-rays
4.sound waves
Which one of the following is nearly monochromatic light ?
1.light form fluorescent tube
2.light form neon lamp
3.light form sodium lamp
4.light form simple lamp