Conductors are materials that allow
1.Allow the flow of heat
2.Does not allow heat to flow
3. Allows cold to flow
4.Stops cold from passing through
In a photoelectric experiment for 4000 Å incident radiation, the potential difference to stop the ejection is 2 V. If the incident light is changed to 3000 Å, then the potential required to stop the ejection of electrons will be
1.2 V
2.Less than 2 V
3.Zero
4.Greater than 2 V
In a single-mode fibre, how does the fraction of energy travelling through bound mode appear in the cladding?
1.As a crescent wave
2.As a gibbous wave
3.As an evanescent wave
4.All of these
Resolving power of a microscope depends upon
1.The focal length and aperture of the eye lens
2.The focal length and objective of the eye lens
3.The apertures of the objective and the eye lens
4.The wavelength of light illuminating the object
Resolving power of light microscope is
1.2 mm
2.0.2 mm
3.0.1 mm
4.1 mm
Two parallel conductors separated by a distance 2r carries current i in the same direction. The intensity of the magnetic field midway between them is
1.Zero
2.μ0 i/r
3.4μ0 i/r
4.μ0 i/4r
What is the inverse of resistance called?
1.Inductance
2.Conductance
3.Resistivity
4.permittivity
What is the ratio of resolving power of an optical microscope for wavelengths λ1= 4000 Å and λ2= 6000 Å?
1.2:3
2.3:2
3.6:25
4.16:9
Which among the following fibre optic cables have a core of size 480 μm to 980 μm and made up of polymethylmethacrylate?
1.Glass fibre optic cable
2.Plastic fibre optic cable
3.Plastic clad silica fibre optic cable
4.All of the above
Which of the following is not due to total internal reflection of light?
1.Brilliance of diamond
2.Mirage formation
3.Optical fibre working
4.Rainbow formation
Which of the following is the most conductive element?
1.Copper
2.Iron
3.Silicon
4.Silver
A cyclotron can accelerate
1.β particles
2.α particles
3.High-velocity gamma rays
4.High-velocity X-rays
A material that has zero resistance is called
1.Insulator
2.Conductor
3.Superconductor
4.semiconductor
A microscope is used to focus on an object at the bottom of a beaker. The microscope is raised by 1 cm. To what height should the water be poured to bring the object in focus again. Refractive index of water is 4/3.
1.1 cm
2.4/3 cm
3.4 cm
4.3 cm
A proton of energy 100 eV is moving perpendicular to a magnetic field 10-4 T. The cyclotron frequency of the proton in radian/sec
1.2.80 x 106
2. 9.6 x 103
3.5.6 x 106
4.1.76 x 106
A ray of light will undergo total internal reflection if it
1.Goes from rarer medium to denser medium
2.Incident at an angle less than the critical angle
3.Strikes the interface normally
4.Incident at an angle greater than the critical angle
A vertical microscope is focused on a point at the bottom of an empty tank. Then water (μ=4/3) is poured into the tank up to a height of 4 cm. After which a liquid that does not mix with water is poured over it up to a height of 2 cm above the water. The refractive index of the liquid is 3/2. What should be the vertical distance through which the microscope must be moved to bring the object in focus again?
1.2.61 cm
2.1.67 cm
3.5 cm
4.4.1 cm
An alternating electric field of frequency f is applied across the dees (radius = R) of a cyclotron that is being used to accelerate protons (mass = m). The operating magnetic field (B) used in the cyclotron and the kinetic energy (K) of the proton, produced by it, are given by
1.B = mf/e and K= 2mπ2v2R2
2.B =2πmf/e and K= m2πvR2
3.B =2πmf/e and K= 2mπ2v2R
4.B = mf/e and K= m2πvR2
Consider a circular conductor with 2m radius and 8 A current flowing through it. What is the value of magnetic field intensity at the centre of the circular conductor?
1.4π x 10-7 T
2.8π x 10-7 T
3.8 x 10-7 T
4.3π x 107 T
Consider a current i flowing through the inner conductor of a coaxial cable and the current returns along the outer conductor of the cable. The value of magnetic induction at a distance r from the axis is
1.(μ0/4π)(2i/r)
2.∞
3.Zero
4. (μ0/4π)(2πi/r)
Cyclotron can be used in
1.Particle therapy to treat cancer
2.Particle therapy to treat cancer
3.Produce short-lived positron-emitting isotopes for PET imaging
4.All of the above
Cyclotron cannot accelerate
1.Electrons
2.Neutrons
3.Positive ions
4.(Both (1) and (2)
Data signal with minimum error is generated by which among the following
1.Signal processing circuits
2.Photodiode
3.Linear circuitry
4.None of the above
Differentiation capacity of a compound microscope is
1.27.5 μm
2.2.75 μm
3.0.275 μm
4.None of the above
Good conductors have many loosely bound
1.Atoms
2.Protons
3.Molecules
4.Electrons
High-frequency long-distance propagation mostly depends on
1.Ionospheric reflection
2.Tropospheric reflection
3.Ground reflection
4.Inverted reflection
If the current I flows through the coil of radius r then the field at the centre of the circular coil is
1.Inversely proportional to I2
2.Directly proportional to I
3.Directly proportional to r
4.Inversely proportional to r2
If the strength of the magnetic field at a point r near a long straight current-carrying wire is B. The value of the field at a distance r/2 will be
1. B/2
2.B/4
3.2B
4.4B
If the work function for a certain metal is 3.2 x 10-19 joule and it is illuminated with light of frequency 8 x 1014 Hz. The maximum kinetic energy of the photo-electrons would be (h= 6.63 x 10-34 Js).
1.2.1 x 10-19 J
2.8.5 x 10-19 J
3.5.3 x 10-19 J
4.3.2 x 10-19 J
In an optical fibre communication system, which among the following is not a typical transmitter function?
1.Coding for error protection
2.Decoding of input data
3.Electrical to optical conversion
4.Recoding to match output standard
In Kirchhoff’s first law Σi = 0 at the junction is based on the conservation of
1.Energy
2.Charge
3.Momentum
4.Speed
In single-mode fibres, the cladding diameter must be at least
1.Five times the core diameter
2.Thrice the core diameter
3.Ten times the core diameter
4.Twice the core diameter
Kirchhoff’s Current Law is based on
1.The charge can be accumulated at the node
2.Charge cannot be accumulated at the node
3.Energy is stored at the node
4.Depending on the circuit charge can be accumulated at the circuit
Light of wavelength 4000 Å is incident on a sodium surface for which the threshold wavelength of photo-electrons is 5420 Å. The work function of sodium is
1.5 eV
2. 3 eV
3.2.29 eV
4. 0.57 eV
Mathematical prediction of radio waves was done by
1.Einstein
2.Hertz
3.Faraday
4.Maxwell
Photocell is a device to
1.Store photons (b) (c) (d)
2.Measure light intensity
3.Convert photon energy into mechanical energy
4.Store electrical energy for replacing storage batteries
Photoelectric effect was explained by
1. Einstein
2.Faraday
3.Plank
4.Hertz
Photoelectrons stopping potential depends on
1.Frequency of incident light and nature of the cathode material
2.The intensity of the incident light
3.The frequency of the incident light
4.Nature of cathode material
Photoelectrons stopping potential depends on
1.Frequency of incident light and nature of the cathode material
2.The intensity of the incident light
3.The frequency of the incident light
4.Nature of cathode material
Radio waves sometimes bend around the corners due to
1.Reflection
2.Diffusion
3.Refraction
4.Diffraction
Radio waves would strongly reflect off
1.A flat insulating surface of the right size
2.A flat metallic surface of the right size
3.A flat dielectric surface of the right size
4.A flat body of water
Suppose a cyclotron is operated at an oscillator frequency of 12 MHz and a dee radius of 53cm. What is the resulting kinetic energy of the deuterons?
1.16.6 MeV
2.12 MeV
3.15 MeV
4.14 MeV
The algebraic sum of voltages around any closed path in a network is equal to
1.Infinity
2.1
3.0
4.Negative polarity
The angular frequency of a cyclotron is independent of
1.Speed
2.Mass
3.Magnetic field
4.Charge
The cyclotron frequency of an electron grating in a magnetic field of 1 T is approximately
1.28 MHz
2.280 MHz
3.2.8 GHz
4.28 GHz
The electric field and magnetic field of a radio wave are
1.Perpendicular to each other
2.Perpendicular to the direction of propagation
3.Both a and b
4.None of the above
The energy gap is maximum in
1.Conductors
2.Semiconductors
3.Insulators
4.Superconductors
The energy of emergent protons in MeV from a cyclotron having a radius of its dees 2 m and applied magnetic field 0.8 T is (mass of proton = 1.67 x 10-27 kg).
1.0.961 x 10-11 J
2.1.22 x 10-11 J
3.1.5 x 10-12 J
4.12 x 10-11 J
The fibres not used nowadays for optical fibre communication system are
1.Single-mode fibre
2.Multimode fibre
3.Coaxial cable
4.Multimode graded-index fibres
The fibres not used nowadays for optical fibre communication system are
1.Single-mode fibre
2.Multimode fibre
3.Coaxial cable
4.Multimode graded-index fibres
The magnetic field due to a copper rod carrying direct current is
1.The magnetic field is inside the rod
2.The magnetic field is outside the rod
3.Both inside and outside the rod
4.Neither inside nor outside
The magnification power of a compound microscope does not depend upon
1.The focal length and aperture of the eye lens
2.The apertures of the objective lens
3.Tube length of the microscope
4.None of the above
The maximum kinetic energy of the positive ion in the cyclotron is
1.qBR2/2m
2.q2B2R2/2m
3.q2B2R2/2m
4.qBR/m
The minimum energy required to remove an electron is called
1.Stopping potential
2.Kinetic energy
3.Work function
4.None of these
The objective and the eye-piece of the compound microscope having a focal length of 0.95 cm and 5 cm, respectively, are kept at a distance of 20 cm. At a distance of 25 cm the large image is formed. Calculate the total magnification.
1.84
2.80
3.94
4.75
The radio waves were demonstrated experimentally by
1.Hertz
2.Maxwell
3.Marconi
4.Armstrong
The resistance of the conductor is directly proportional to
1.Length
2.Area of cross-section
3.Temperature
4.resistivity
The speed of radio wave in free space is
1.3 x 106 metres/second
2.3 x 108 metres/second
3.3 x 106 miles/second
4.3 x 108 miles/second
The stopping potential value is 0.6 V when the light source is kept at a distance of 20 cm. When the source is kept at 40 cm away, the stopping potential will be
1.0.6 V
2.0.3 V
3.1.2 V
4.2.4 V
The terminal potential difference will be greater than its emf when it is
1.In open circuit
2.Being charged
3.Being charged or discharged
4.Being discharged
To which law of electricity is Biot Savart law of magnetism analogous to
1.Coulomb’s law
2.Ohm’s law
3.Kirchoff’s law
4.Faraday’s law
Two identical glass (μg=3/2) equi – convex lenses of focal length f each are kept in contact. The space between the two lenses is filled with water ((μw=4/3). The focal length of the combination is
1.f/3
2.f
3.4f/3
4.3f/4
Using a microscope a glass plate of 5 mm is viewed from the above. The microscope is lowered by 3 mm to view the bottom surface of the glass. What is the refractive index of the glass?
1.2
2.1.66
3.2.25
4.1.4
What is the distance from the far end of the ground wave to the nearest point where the sky wave returns to earth called?
1.Angle of radiation
2.maximum usable frequency
3.Skip distance
4.Skip zone
What is the value of the maximum kinetic energy acquired by electron due to radiation of wavelength 100 nm?
1.12 eV
2.6.2 eV
3.100 eV
4.300 eV
When the cells are connected in parallel, then
1.The current increases
2.The current decreases
3.The emf increases
4.The emf decreases
Which among the following is described by the concept of numerical aperture in an optical fibre?
1.Light collection
2. Light scattering
3.Light dispersion
4.Light polarisation
Which among the following is not an insulator?
1.Wool
2.Plastic
3.Silver
4.Paper
Which basic law should be followed to analyse the circuit?
1.Newton’s law
2.Faraday’s law
3.Amperes law
4.Kirchoff’s law
Which is the equation of the magnetic field according to Biot-Savart’s law?
1.IdIsinθ/r2
2. (μ0/4π)IdIsinθ/r
3. (μ0/4π)IdIsinθ/r2
4.(μ0/4π)IdIsinθ
Which of the following are electromagnetic
1.Radio waves
2.Light
3.Gamma waves
4.All the above
Which of the following is the phenomenon caused when Radio waves travel in two or more paths during propagation and produce slowly-changing phase differences between signals?
1.Absorption
2.Fading
3.Baffling
4.skip
Which of the following properties cannot be calculated from Biot Savart law?
1.Magnetic field intensity
2.Flux density
3.Permeability
4.Electric field intens
Why is copper a preferred choice in making electrical wires?
1.Copper is a good conductor of electricity
2.Poor conductors of electricity
3.Insulators
4.Superconductor
With the increase in temperature the resistance of semiconductors
1.Decreases
2.Increases
3.Remains constant
4.Initially increases and then decreases