31.

The impedance of a circuit, when a resistance R and an inductor of inductance L are connected in series in an AC circuit of frequency f, is

• $\sqrt{\mathrm{R} + 2 {\mathrm{\pi }}^2 {\mathrm{f}}^2 {\mathrm{L}}^2}$

• $\sqrt{\mathrm{R} + 4{\mathrm{\pi }}^2 {\mathrm{f}}^2 {\mathrm{L}}^2}$

• $\sqrt{{\mathrm{R}}^2 + 4 {\mathrm{\pi }}^2 {\mathrm{f}}^2 {\mathrm{L}}^2}$

• $\sqrt{{\mathrm{R}}^2 + 2{\mathrm{\pi }}^2 {\mathrm{f}}^2 {\mathrm{L}}^2}$

Which of the following electromagnetic waves have the  smallest wavelength?

• γ - rays

• X- rays

• UV waves

• infrared rays

A plane mirror produces a magnification of

• zero

• -1

• +1

• between 0 and +1

Two coherent light beams of intensities I and 4I are superposed. The maximum and minimum possible intensities in the resulting beam are

• 5I and I

• 5 I and 3 I

• 9 I and I

• 9 I and 3 I

The kinetic energy of an electron, which is accelerated in the potential difference of 100 V, is

• 1.6 × 10^-17 J

• 1.6 × 10^-14 J

• 1.6 × 10^-10 J

• 1.6 × 10^-8 J

J.J. Thomson's cathode ray tube experiment demonstrated- that

• cathode rays are streams of negatively charged ions

• all the mass of an atom is essentially in the nucleus

• the e/m of electrons is much greater than the e/m of protons.

• the e/m ratio of the cathode ray particles changes when a different gas is placed in the discharged tube

Wavelength of light emitted from second orbit to first orbit in a hydrogen atom is

• 6563 A^o

• 4102 A^o

• 4861 A^o

• 1215 A^o

The half-life of a radio-isotope is 4h. If initial mass of the isotope was 200 g, then mass remaining after 24 h will be

• 1.042 g

• 2.084 g

• 3.125 g

• 4.167 g

If ₈₂U²³⁸ emits 8 $\mathrm{\alpha }$ - particles and 6 β - particles, then the resulting nucleus is

• ₈₂U²⁰⁶

• ₈₂Pb²⁰⁶

• ₈₂U²¹⁰

• ₈₂U²¹⁴

Which logic gate is represented by the following combination of logic gates?

• OR

• NOR

• AND

• NAND