Physics

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Showing 126 to 150 of 1648 questions (page 6 of 66).

126. The stopping potential in a photoelectric experiment depends on

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

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

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

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

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

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

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

130. Laser action requires

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

131. 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. nuclear decay D. thermal emission from the filament E. stimulated emission

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

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

133. Isotopes of an element have the same

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

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

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

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

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

136. The energy released in nuclear reactions arises from

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

137. Energy production in the Sun is mainly due to

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

138. Which radiation has the greatest penetrating power?

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

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

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

140. How many base units are defined in the International System of Units (SI)?

A. 5 B. 6 C. 7 D. 8 E. 9

141. The dimensions of Planck's constant are the same as those of

A. energy B. power C. linear momentum D. angular momentum E. force

142. A screw gauge has a pitch of 0.5 mm and 50 divisions on its circular scale. Its least count is

A. 0.5 mm B. 0.05 mm C. 0.01 mm D. 0.001 mm E. 0.025 mm

143. Which of the following is a supplementary unit in SI?

A. newton B. radian C. kelvin D. mole E. joule

144. The dimensional formula of pressure is

A. [ML-1T-2] B. [MLT-2] C. [ML2T-2] D. [ML-3T0] E. [ML-2T-2]

145. If a quantity is measured as 4.0 cm with an absolute uncertainty of 0.1 cm, the percentage uncertainty is

A. 0.25% B. 2.5% C. 4% D. 25% E. 0.4%

146. A dimensionally correct equation

A. is always physically correct B. must be numerically correct C. may still be physically incorrect D. cannot contain constants E. always contains a trigonometric term

147. A unit vector perpendicular to the plane containing vectors A and B is given by

A. A.B B. (A x B)/|A x B| C. A + B D. (A.B)/|A||B| E. A - B

148. The value of i . (j x k) is

B. 1 C. -1 D. i E. j

149. Two forces of 10 N each act on a body with an angle of 120 degrees between them. The magnitude of the resultant is

A. 0 N B. 10 N C. 17.3 N D. 20 N E. 14.1 N

150. If A + B = A - B, then vector B must be

A. a unit vector B. parallel to A C. perpendicular to A D. a null vector E. equal to A

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