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NEET Physics Solved Question Paper 2013

Multiple Choice Questions

41.

If modulation index is 1/2 and power of carrier wave is 2 W. Then what will be the total power in modulated wave?

0.5 W
1 W
0.25 W
2.25 W

42.

If velocity of a particle is three times of that of electron and ratio of de Broglie wavelength of particle to that of electron is 1.814 x 10^-4. The particle will be

Neutron
Deuteron
Alpha
Tritium

43.
In an intrinsic semiconductor band gap is 1.2 eV then ratio of number of charge carriers at 600 K and 300 K is

10⁴

10⁷

10⁵

10³

10⁵

We have formula

n_i = n₀ exp $[- \frac{E_{g}}{2 K_{B} T}]$

wher K_B- Boltzmann constant = 8.62 × 10^-5 eV/K

T - temperature

n₀ - constant

Initial temperature T₁ = 300 K

The intrinsic carrier concentration at this temperature is written as

$n_{i_{1}} = n_{0} \exp [- \frac{E_{g}}{2 k_{B} \times 300}]$ ......(i)

Final temperature T₂ = 600 K

The intrinsic carrier combination at this temperature is written as

$n_{i_{2}} = n_{0} \exp [- \frac{E_{g}}{2 k_{B} \times 600}]$ ........(ii)

The ratio between the conductivities at 600K and 300 K is equal to between the intrinsic carriers concentrations at these temperatures

$\frac{n_{2}}{n_{1}} = \frac{n_{0} \exp [- \frac{E_{g}}{2 k_{B} 600}]}{n_{0} \exp [- \frac{E_{g}}{2 k_{B} 300}]}$

= exp $\frac{E_{g}}{2 k_{B}} [\frac{1}{300} - \frac{1}{600}]$

= $[\frac{1.2}{2 \times 8.62 \times 10^{- 5}} \times \frac{2 - 1}{600}]$

= exp [11.6]

$\frac{n_{2}}{n_{1}} =$ 1.09 × 10⁵ ≈ 10⁵

44.

Long distance communication between two point or earth is achieved by

Space wave communication
Sky wave communication
Satellite wave communication
Line of sight transmission

45.

Polaroid glass is used in sun glasses because

it reduces the light intensity to half on account of polarisation
it is fashionable
it has good colour
it is cheaper

46.

Which of the following statement is incorrect?

Neutron is less stable than proton
Neutron can cause fission in nuclear reactors but proton can not.
A free proton can emit beta particle.
A bound proton can emit beta particle.

47.

Electric field at a distance r from infinitely long conducting sheet is proportional to

r^-1
r^-2
r^-3/2
independent of r

48.

In a Young's double slit experiment the spacing between the slits is 0.3 mm and the screen is kept at a distance of 1.5 m. The second bright fringe is found 6 mm from the central fringe. The wavelength of the light used in the experiment is