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Showing 1701 to 1725 of 3046 questions (page 69 of 122).

1701. The output of an XOR gate is high when

A. the inputs are different B. either input is low C. both inputs are high D. the inputs are the same E. both inputs are low

1702. In a common emitter transistor amplifier, the current gain beta is the ratio of

A. collector current to base current B. base current to collector current C. emitter current to base current D. collector voltage to base voltage E. collector current to emitter current

1703. According to special relativity, a moving clock runs

A. only at the speed of light B. backwards C. slower than a stationary clock D. faster than a stationary clock E. at the same rate

1704. The energy equivalent of mass m is

A. m/c2 B. mc2 C. m2c D. mc E. (1/2)mc2

1705. Photoemission does not occur if the incident light has a frequency below the

A. stopping potential B. cut off wavelength C. Rydberg frequency D. threshold frequency E. Compton frequency

1706. The wave nature of electrons was confirmed experimentally by

A. Rutherford's scattering experiment B. the photoelectric experiment C. Millikan's oil drop experiment D. Michelson's interferometer E. the Davisson and Germer electron diffraction experiment

1707. The momentum of a photon of wavelength lambda is

A. hc/lambda B. h/c lambda C. h/lambda D. h lambda E. lambda/h

1708. The work function of a metal is commonly expressed in

A. electron volts B. watts C. hertz D. coulombs E. joules only

1709. The Lyman series of hydrogen lies in the

A. microwave region B. infrared region C. visible region D. X-ray region E. ultraviolet region

1710. The energy of the electron in the second Bohr orbit of hydrogen is

A. -13.6 eV B. -0.85 eV C. -6.8 eV D. -3.4 eV E. -1.51 eV

1711. In alpha decay, the mass number and atomic number of the nucleus change by

A. -4 and -2 B. -4 and +2 C. -2 and -4 D. -1 and 0 E. 0 and -1

1712. The SI unit of radioactive activity is

A. sievert B. becquerel C. gray D. roentgen E. curie

1713. Radiocarbon dating of organic remains uses the isotope

A. potassium 40 B. uranium 238 C. carbon 12 D. carbon 13 E. carbon 14

1714. Nuclear forces are

A. short range and charge independent B. long range and charge dependent C. identical to electrostatic forces D. effective only between protons E. weaker than gravitational forces

1715. The minimum mass of fissile material required to sustain a chain reaction is called the

A. mass defect B. threshold mass C. critical mass D. binding mass E. atomic mass

1716. Cobalt 60 is used in medicine mainly as a source of

A. neutrons B. beta particles C. X-rays D. alpha particles E. gamma rays for radiotherapy

1717. A radioactive sample of initial activity A0 has a half life T. Its activity after time 4T is

A. A0/8 B. A0/4 C. A0/2 D. A0/16 E. A0/32

1718. The molar mass of carbon dioxide is

A. 48 g mol-1 B. 44 g mol-1 C. 12 g mol-1 D. 28 g mol-1 E. 32 g mol-1

1719. One atomic mass unit is equal to

A. 1.661 x 10^-24 kg B. 9.1 x 10^-31 kg C. 6.02 x 10^-23 kg D. 1.661 x 10^-27 kg E. 1.6 x 10^-19 kg

1720. The total number of atoms in one mole of methane is

A. 1.204 x 10^24 B. 3.01 x 10^24 C. 2.41 x 10^24 D. 6.02 x 10^23 E. 5 x 10^23

1721. The molecular formula of a compound is related to its empirical formula by

A. multiplication by a whole number B. addition of a constant C. subtraction of hydrogen D. the ratio of densities only E. division by a whole number

1722. Percentage yield is calculated as

A. actual yield minus theoretical yield B. moles of product times 100 C. actual yield divided by theoretical yield times 100 D. mass of reactants divided by mass of products E. theoretical yield divided by actual yield times 100

1723. Distillation under reduced pressure is used for liquids that

A. are immiscible with water B. decompose at their normal boiling points C. form no vapour D. have very low boiling points E. are highly volatile

1724. A desiccator is used to

A. distil liquids B. weigh precipitates C. dissolve solids D. keep substances free from moisture while cooling E. heat substances strongly

1725. A sharp and constant melting point is used as a criterion of

A. purity B. density C. solubility D. conductivity E. volatility

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