Physics

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Showing 851 to 875 of 1648 questions (page 35 of 66).

851. For a transistor operating as an amplifier, the emitter base junction and collector base junction are

A. both reverse biased B. unbiased C. reverse and forward biased respectively D. both forward biased E. forward and reverse biased respectively

852. Doping silicon with a pentavalent impurity produces

A. an n-type semiconductor B. an insulator C. an intrinsic semiconductor D. a p-type semiconductor E. a superconductor

853. According to the special theory of relativity, the speed of light in free space is

A. dependent on the observer velocity B. infinite C. different for different observers D. the same for all inertial observers E. dependent on the source velocity

854. In the photoelectric effect, the maximum kinetic energy of the emitted electrons is

A. hf B. independent of frequency C. hf - work function D. hf + work function E. work function - hf

855. The de Broglie wavelength of a particle of momentum p is

A. h/p B. h/p2 C. hp D. p/h E. h p2

856. The Compton effect demonstrates the

A. wave nature of light B. polarization of X-rays C. interference of X-rays D. particle nature of light E. transverse nature of light

857. Heisenberg's uncertainty principle states that the product of the uncertainties in position and momentum is

A. equal to hf B. at least of the order of h/(4 pi) C. zero D. independent of h E. at most h

858. The stopping potential in a photoelectric experiment depends on

A. the polarization of light B. the distance of the source C. the intensity of light only D. the frequency of light and the material E. the area of the cathode

859. According to Bohr's theory, the angular momentum of an electron in the nth orbit is

A. n2 h B. nh/(2 pi) C. h/(2 pi n) D. h/n E. nh

860. The spectral series of hydrogen that lies in the visible region is the

A. Lyman series B. Pfund series C. Balmer series D. Brackett series E. Paschen series

861. The ionization energy of a hydrogen atom in its ground state is

A. 10.2 eV B. 27.2 eV C. 1.51 eV D. 3.4 eV E. 13.6 eV

862. Laser action requires

A. population inversion B. thermal equilibrium C. a very low pumping rate D. a single energy level E. incoherent sources

863. The continuous part of an X-ray spectrum is produced by

A. electron transitions between inner shells B. deceleration of fast electrons in the target C. thermal emission from the filament D. nuclear decay E. stimulated emission

864. The radius of the nth Bohr orbit in hydrogen is proportional to

A. n2 B. n3 C. 1/n D. n E. 1/n2

865. Isotopes of an element have the same

A. atomic mass B. mass number C. binding energy D. atomic number E. number of neutrons

866. A radioactive sample has a half life of 10 days. The fraction remaining after 30 days is

A. 1/4 B. 1/3 C. 1/2 D. 1/16 E. 1/8

867. In beta minus decay, the atomic number of the nucleus

A. decreases by 2 B. decreases by 1 C. increases by 1 D. increases by 2 E. remains unchanged

868. The energy released in nuclear reactions arises from

A. frictional heating B. electron transitions C. chemical bonding D. mass defect E. ionization

869. Energy production in the Sun is mainly due to

A. radioactive decay of uranium B. gravitational contraction alone C. nuclear fusion D. nuclear fission E. chemical combustion

870. Which radiation has the greatest penetrating power?

A. beta B. gamma C. alpha D. proton E. neutron in air only

871. In a nuclear reactor, the moderator is used to

A. slow down fast neutrons B. shield the operators C. increase the fuel temperature D. control the coolant flow E. absorb excess neutrons

872. Which quantity has the same dimensions as work?

A. power B. impulse C. torque D. force E. pressure

873. The number of significant figures in 1.230 x 10^4 is

A. 3 B. 4 C. 6 D. 2 E. 5

874. The sum of 2.50 cm and 1.6 cm, expressed to the correct number of decimal places, is

A. 4 cm B. 4.16 cm C. 4.10 cm D. 4.100 cm E. 4.1 cm

875. One radian is approximately equal to

A. 180 degrees B. 6.28 degrees C. 1 degree D. 57.3 degrees E. 3.14 degrees

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