Description : The minimum frequency required to eject electrons from a metallic surface is called a) Critical frequency b) Peak value of frequency c) Threshold frequency d)Photo frequency
Last Answer : c) Threshold frequency
Description : When a certain beam of light falls upon a metal surface, it ejects photoelectrons from it. The number of photoelectrons ejected per second by the beam of light depends upon one of the following. Is it ... the work function of the metal y) the frequency of the beam z) the intensity of the beam
Last Answer : ANSWER: Z -- THE INTENSITY OF THE BEAM
Description : The energy required to completely remove an electron from the first Bohr orbit is called a) excited energy b) ionization energy c) accelerated energy d) orbital energy
Last Answer : b) ionization energy
Description : The amount of energy required to completely remove an electron from the first Bohr orbit is a) 13.6 MeV b) 13.6 eV c) 1.36 MeV d) 1.36 eV
Last Answer : b) 13.6 eV
Description : The minimum charge on any electron be less than: (a) 1.6×10−19C (b) 3.2×10−19C (c) 1.8×10−19C (d) 9.1×10−19C
Last Answer : (a) 1.6×10−19C
Description : The magnitude of saturation photo electric current depends upon (a) Frequency (b) Intensity (c) Work function (d) Stopping potential
Last Answer : Ans:(b)
Description : The force per unit charge is called: (a) Electric field (b) Electric field intensity (c) Electric potential energy (d) Electric potential
Last Answer : b) Electric field intensity
Description : The threshold frequency is the frequency below which – (1) photo current increases with voltage (2) photo current decreases with voltage (3) photo electric emission is not possible (4) photo current is constant
Last Answer : (3) photo electric emission is not possible Explanation: The photoelectric effect is the emission of electrons by substances, especially metals, when light falls on their surfaces. The photoelectric ... gain sufficient energy to overcome the electrostatic barrier of the work function of the metal.
Description : The threshold frequency is the frequency below which - (1) photo current is constant (2) photo current increases with voltage (3) photo current decreases with volt (4) photo electric emission is not possible
Last Answer : (4) photo electric emission is not possible
Description : The threshold frequency is the frequency below which : (1) photo current increases with voltage (2) photo current decreases with voltage (3) photo electric emission is not possible (4) photo current is constant
Last Answer : photo electric emission is not possible
Description : The minimum amount of energy required for the reaction to takes place is called threshold energy.
Last Answer : What is activation energy ?
Description : The total energy of electron in the Bohr orbit is given by the formula, E = a) - ke2 /2r b) - ke2 /2r2 c) - k 2 e/2r d) - ke2 /r
Last Answer : a) - ke2 /2r
Description : If energy of incident photon is greater than the rest mass energy of electron positron pair, the surplus energy is shared by the pair as, a) Potential energy b) Thermal energy c) Electronic energy d) Kinetic energy
Last Answer : d) Kinetic energy
Description : The minimum energy required to allow a chemical reaction to proceed is termed as the 'threshold energy '. Chemical reactions with low activation energy are: (A) Always irreversible (B) Insensitive to temperature changes (C) Mostly irreversible (D) Highly temperature sensitive
Last Answer : (B) Insensitive to temperature changes
Description : Whichofthe followingterms describesthe reason thatlightisrefractedat different angles? a. Photon energy changes with wavelength b. Light is refracted as a function of surface smoothness c. The angle is determined partly by a and b d. The angle is determined by the index of the materials
Last Answer : d. The angle is determined by the index of the materials
Description : The space around the charge within which other charges are influenced by it is called: (a) Electric field (b) Magnetic field (c) Electric flux (d) Electric intensity
Last Answer : a) Electric field
Description : The number of electric field lines passing through a certain element of area is called: (a) Electric lines of force (b) Electric intensity (c) Electric flux (d) None of these
Last Answer : (c) Electric flux
Description : The ratio of intensity of magnetisation to the magnetisation force is known as (a) flux density (b) susceptibility (c) relative permeability (d) none of the above
Last Answer : (b) susceptibility
Description : Which of the following is a vector quantity ? (a) Relative permeability (b) Magnetic field intensity (c) Flux density (d) Magnetic potential
Last Answer : (b) Magnetic field intensity
Description : The unit of electric intensity is
Last Answer : Volt/ metre
Description : A sensor which changes light intensity into electric voltage. (a) LDR (b) thermistor (c) photodiode (d) photovoltaic
Last Answer : (a) LDR
Description : The electric intensity at a distance of 1m from the point charge is 1μC is: (a) 9 × 109 N/C (b) 9 × 106 N/C (c) 9 × 103 N/C (d) 9 N/C
Last Answer : c) 9 × 103 N/C
Description : A charge of 2 coulomb is in a field of intensity 2 N/C. The force on charge is: (a) 4 π N (b) 4 N (c) 0 N (d) 1 N
Last Answer : b) 4 N
Description : The electric intensity is a: (a) Scalar quantity (b) Vector quantity (c) Physical quantity (d) None of above
Last Answer : (b) Vector quantity
Description : The reverse process of photo-electric effect is called: a) Annihilation of matter b) Compton effect c) Pair production d) X-rays
Last Answer : d) X-rays
Description : A device based on photo electric effect is called a) Photo sensitive b) Photo diode c) Photo synthesis d) Photo cell
Last Answer : d) Photo cell
Description : The photo copying process is called: (a) Xerography (b) Inkjet printer (c) Both (a) and (b) (d) None of these
Last Answer : (a) Xerography
Description : Pick up the correct statement from the following: (A) The minimum frequency of light for which no electrons are emitted, is called threshold frequency (B) Polarising angle of glass is 57.5° (C) At the polarising angle, the reflected and refracted rays are orthogonal (D) All the above
Last Answer : Answer: Option D
Description : What is a photo cell?*
Last Answer : A cell whose resistance varies with intensity of light.
Description : If electron has to be confined in the nucleus, its speed would have to be greater than a) 1010 cm/s b) 1010 m/s c) 1020 m/s d) 1020 cm/s
Last Answer : b) 1010 m/s
Description : Electron can exist in the atom but outside the nucleus because a) speed of electron is equal to the speed of light b) speed of electron is more than speed of light c) speed of electron is less than speed of light d) None of these
Last Answer : c) speed of electron is less than speed of light
Description : The quantized Bohr orbit radius of electron in hydrogen atom is given by a) n2 r3 b) nr1 c) n2 r2 d) n2 r1
Last Answer : d) n2 r1
Description : The speed of hydrogen electron in the nth orbit is given by vn = a) 2λke2 / nh b) 2πke2 / λh c) 2πke2 / nh d) 2πke2 / h
Last Answer : c) 2πke2
Description : A three dimensional image is obtained by a)Electron microscope b) Scanning electron microscope c) Magnetic imaging d)None of these
Last Answer : b) Scanning electron microscope
Description : The electron was discovered by a) Burcherer b) Anderson c) Chadwick d) J. J Thomson
Last Answer : d) J. J Thomson
Description : An electron moves with a velocity of 2 × 106 ms-1 in the direction of a uniform magnetic field of 0.8 Tesla. The force on electron is a) 8 N b) 2 N c) 4 N d) Zero
Last Answer : d) Zero
Description : A circuit which develops voltage across the horizontal deflection plates is known as a) Time base generator b) Electron gun c) Thermionic diode d) Zener diode
Last Answer : a) Time base generator
Description : ___________ is not affected by a magnetic field a) Change in magnetic flux b) a moving electron c) a stationary proton d) current flowing in a conductor
Last Answer : c) a stationary proton
Description : Two electron beams move parallel to each other. The nature of force between them is a) Attractive b) Repulsive c) Dependent on magnitude of velocity d) None
Last Answer : b) Repulsive
Description : An electron and a neutron enter a magnetic field with the same velocity. Ratio of electron to neutron’s acceleration is a) mn me b) √ mn me c) √ me mn d) me
Last Answer : a) mn me
Description : Define : (i)Threshold frequency (ii)Work function
Last Answer : Threshold frequency: The minimum frequency of incident radiation at which emission of photoelectrons starts is called Threshold frequency. Work function: The amount of energy required to detach the electron from metal surface is called work function.
Description : The emission of number of photo electrons depends upon a) The colour of the body b) The frequency of incident light c) The intensity of light d) All of the above
Last Answer : c) The intensity of light
Description : The energy required to magnetize and demagnetize is called a) Saturation b) Retentivity c) Coercivity d) Hysteresis loss
Last Answer : d) Hysteresis loss
Description : True statement about dark adaptation include: a. the threshold for light intensity falls b. it is biphasic c. the initial adaptation is due to rod adaptation d. the change in the light intensity threshold is usually around 100 folds
Last Answer : the threshold for light intensity falls
Description : Arange ofmicrowave frequenciesmore easilypassed bythe atmospherethan are theothersis called a a.window b. critical frequency c. gyro frequency range d. resonance in the atmosphere
Last Answer : a.window
Description : Themechanicalsplice isbestsuited for a. quicker installation under ideal conditions b. minimum attenuation losses c. field service conditions d. situations in which cost of equipment is not a factor
Last Answer : c. field service conditions
Description : In the plane of AC generator coil is parallel to the field, then emf induced in coil is: a. maximum b. minimum c. zero d. intermediate
Last Answer : b. minimum
Description : In the plane of the A.C generator coil is perpendicular to the field, then induced emf in the coil is: a. Maximum b. minimum c. zero d. intermediate value