Physics

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Showing 1276 to 1300 of 1648 questions (page 52 of 66).

1276. The Compton effect demonstrates the

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

1277. Heisenberg's uncertainty principle states that the product of the uncertainties in position and momentum is

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

1278. The stopping potential in a photoelectric experiment depends on

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

1279. According to Bohr's theory, the angular momentum of an electron in the nth orbit is

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

1280. The spectral series of hydrogen that lies in the visible region is the

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

1281. The ionization energy of a hydrogen atom in its ground state is

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

1282. Laser action requires

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

1283. The continuous part of an X-ray spectrum is produced by

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

1284. The radius of the nth Bohr orbit in hydrogen is proportional to

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

1285. Isotopes of an element have the same

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

1286. A radioactive sample has a half life of 10 days. The fraction remaining after 30 days is

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

1287. In beta minus decay, the atomic number of the nucleus

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

1288. The energy released in nuclear reactions arises from

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

1289. Energy production in the Sun is mainly due to

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

1290. Which radiation has the greatest penetrating power?

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

1291. In a nuclear reactor, the moderator is used to

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

1292. Which quantity has the same dimensions as work?

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

1293. The number of significant figures in 1.230 x 10^4 is

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

1294. The sum of 2.50 cm and 1.6 cm, expressed to the correct number of decimal places, is

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

1295. One radian is approximately equal to

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

1296. Two vectors of magnitudes 3 and 4 units give a resultant of 7 units. The angle between them is

A. 90 degrees B. 0 degrees C. 45 degrees D. 180 degrees E. 120 degrees

1297. The cross product of a vector with itself is

A. undefined B. twice the vector C. the null vector D. its magnitude squared E. a unit vector

1298. The magnitude of the cross product of two vectors of magnitudes 2 and 3 units with 30 degrees between them is

A. 3 C. 5.2 D. 6 E. 1.5

1299. A force of 5 N acts perpendicular to a spanner at a distance of 0.2 m from the pivot. The torque produced is

A. 10 N m B. 5 N m C. 0.04 N m D. 1 N m E. 25 N m

1300. The projection of vector A along vector B is given by

A. A x B B. A.B C. A.B / |B| D. A.B / |A| E. |A| |B|

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