Physics

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Showing 626 to 650 of 1648 questions (page 26 of 66).

626. The energy equivalent of mass m is

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

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

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

628. The wave nature of electrons was confirmed experimentally by

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

629. The momentum of a photon of wavelength lambda is

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

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

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

631. The Lyman series of hydrogen lies in the

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

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

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

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

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

634. The SI unit of radioactive activity is

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

635. Radiocarbon dating of organic remains uses the isotope

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

636. Nuclear forces are

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

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

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

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

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

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

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

640. The dimensional formula of Young's modulus is

A. [ML2T-2] B. [MLT-2] C. [M0L0T0] D. [ML-1T-2] E. [ML-2T-1]

641. A set of measurements that are closely grouped but far from the true value is described as

A. accurate but not precise B. both accurate and precise C. free from systematic error D. neither accurate nor precise E. precise but not accurate

642. A vernier scale has 10 divisions coinciding with 9 divisions of a main scale graduated in millimetres. The least count is

A. 0.1 mm B. 0.9 mm C. 1 mm D. 0.01 mm E. 0.05 mm

643. Which of the following pairs does not have the same dimensions?

A. work and torque B. force and energy C. impulse and momentum D. frequency and angular velocity E. stress and pressure

644. If the rectangular components of a vector are equal in magnitude, the vector makes an angle with the x-axis of

A. 0 degrees B. 30 degrees C. 60 degrees D. 90 degrees E. 45 degrees

645. The magnitude of the vector 3i + 4j - 12k is

A. 13 B. 12 C. 5 D. 19 E. 7

646. The torque of a force about an axis is zero when the line of action of the force

A. is parallel to the displacement B. has maximum magnitude C. passes through the axis D. acts at the rim E. is perpendicular to the axis

647. The single force that balances a set of concurrent forces is called the

A. couple B. resultant C. normal reaction D. component E. equilibrant

648. For two vectors A and B, the relation between A x B and B x A is

A. A x B = 2 B x A B. A x B = -B x A C. they are equal D. both are zero E. they differ in magnitude only

649. Newton's third law action and reaction forces

A. occur one after the other B. act in the same direction C. are unequal in magnitude D. act on different bodies and do not cancel E. act on the same body and cancel

650. Newton's first law of motion gives the definition of

A. inertia B. weight C. impulse D. momentum E. force

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