The given figure shows the various propagation modes of e . m . waves in communication. Why transmission of TV signals via sky wave is not possible?

In the given question we have to use the concept of Sky waves and apply it to solve the given question. Sky waves cannot be used in transmitting TV signals having frequency more than 80 MHz, because these waves are not reflected back by the ionosphere and penetrate into the outer space. Hence, above will be the correct answer of the given question.

The temperature dependence of resistivity of a material is shown below: b Write the relation between resistivity and average collision time for electron.

The average of velocities of all electrons just after collisions is 0, as they get bounced in all random directions. Hence, the average velocity of an electron along the length of a resistor or conductor wire is equal to that gained due to electrostatic field E. So the required relation is v = eJρτ m ⇒ τ = mv eJρ .

The given figure shows the various propagation modes of e . m . waves in communication. a Write the names of propagation modes in A , B , C .

In the given question we have to use the concept of different modes of propagation and apply it to solve the given question. The name of propagation of A, B and C are Ground wave propagation, space wave propagation and sky wave propagation respectively. Hence, the above will be the correct answer of the given question.

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A silicon specimen is made into a $p$ -type semiconductor by doping, on an average, one indium atom per ${5 \times 10}^{7}$ silicon atoms. If the number density of atoms in the silicon specimen is ${5 \times 10}^{28}$ atoms $m^{- 3}$ , then the number of acceptor atoms in silicon per cubic centimeter will be

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Important Questions on Semiconductor Devices

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

In an intrinsic semi conductor at room temperature number of electrons and holes are

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

As the temperature of the semiconductor is increased, the mobility of electrons and holes

HARD

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

In a semiconductor, the number density of intrinsic charge carriers at

27 ° C

1.5 \times 10^{16} m^{- 3}

. If the semiconductor is doped with an impurity atom, the hole density increases to

4.5 \times 10^{22} m^{- 3}

. The electron density in the doped semiconductor is _______

\times 10^{9} m^{- 3}

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

The charge carriers in an electrolyte are

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

Which of the following statements is incorrect?

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Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

With the increase of temperature, the resistivity of a semiconductor :

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

In a semiconductor, the conductivity increases with the increase in temperature due to

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

The given figure shows the various propagation modes of $e . m$ . waves in communication.

Question Image

Why transmission of TV signals via sky wave is not possible?

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

In a semiconductor crystal, if the current flows due to breakage of crystal bonds, then the semiconductor is called:

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

The energy gap is much more in silicon than in germanium because

MEDIUM

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

The contribution to the total current in a semiconductor, due to electrons and holes are

0.75

and

0.25

respectively. The drift velocity of electrons is

\frac{3}{2}

times that of holes at this temperature. Then the ratio between electron concentration and hole concentration is

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

At a certain temperature, the number density of charge carriers in a semiconductor is

n

. When an electric field is applied to it, the charge carriers drift with an average speed

v

. If the temperature of the semiconductor is raised.

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

Identify the logic gate and write its Boolean expression.

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Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

In a semiconductor, the electrical conductivity is due to

MEDIUM

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

For a transistor the emitter current is

0.505 mA

and the base current is

5.0 μA

. The collector is

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

The temperature dependence of resistivity of a material is shown below:

Question Image

$(b)$ Write the relation between resistivity and average collision time for electron.

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

The given figure shows the various propagation modes of $e . m$ . waves in communication.

Question Image

$(a)$ Write the names of propagation modes in $A, B, C$ .

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

The intrinsic carrier concentration of silicon sample at

300 K

1.5 \times 10^{16} / m^{3} .

What is the density of minority carrier? (after doping, the number of majority carriers is

5 \times 10^{20} / m^{3})

EASY

Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

An intrinsic semiconductor is:

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Physics>Modern Physics>Semiconductor Devices>Intrinsic Semiconductors

The conductivity of a semiconductor sample having electron concentration of

5 \times 10^{18} electrons m^{- 3}

, hole concentration of

5 \times 10^{19} holes m^{- 3}

, electron mobility of

2 .0 m^{2} V^{- 1} s^{- 1}

and hole mobility of

0.01 m^{2} V^{- 1} s^{- 1}

is

(Take charge of an electron as

1 .6 \times 10^{- 19} C

)

A silicon specimen is made into a p-type semiconductor by doping, on an average, one indium atom per 5×107 silicon atoms. If the number density of atoms in the silicon specimen is 5×1028 atoms m-3, then the number of acceptor atoms in silicon per cubic centimeter will be

Important Questions on Semiconductor Devices

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