41.

An electron is moving with velocity v in the direction of magnetic field B, then force acting on electron is

• zero

• e (v x B)

• e (B x v)

• 200 J

Ten wires each of resistance 1 Ω are connected in parallel, then total resistance will be

• 10 Ω

• 1 Ω

• 0.1 Ω

• 0.001 Ω

Wavelength of the particle whose momentum is p

• $\frac{\mathrm{h}}{\mathrm{p}}$

• hp

• $\frac{\mathrm{p}}{\mathrm{h}}$

• p + h

Which of the following has same dimensions to that of Planck's constant?

• Work

• Energy

• Linear momentum

• Angular momentum

Half-life of radium is 1600 yr, then its 1/16th part will remain undecayed after

• 1200 yr

• 6400 yr

• 1800 yr

• 2200 yr

When a light beam enters into water from air, then which of the following does not change?

• Velocity

• Frequency

• Wavelength

• Amplitude

n-type semiconductor is

• positive charged

• neutral

• negatively charged

• None of the above

Atomic number of an atom is Z and mass number is m, then number of neutrons in its nucleus is

• m − Z

• $\frac{\mathrm{m}}{\mathrm{Z}}$

• m + Z

• m × Z

Nucleus of an atom has

• e and n

• e and p

• p and n

• e, p and n

In nth orbit of hydrogen atom energy $\mathrm{E} = \frac{- 13.6}{{\mathrm{n}}^2} \mathrm{eV}$, then energy required to displace  electrons from n = 1 to n = 2 is

• - 10.2 eV

• 3.4 eV

• - 13.6 eV

• 1.51 eV