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PHXII08:ELECTROMAGNETIC WAVES

368901 Assertion :
Propagation of electromagnetic waves (of $2 M H z$ to $30 M H z$ ) is done by Sky wave method.
Reason :
These waves are reflected back to earth by ionosphere.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Ionosphere her its refrective index $(n)$ given by $n = n_{o} {[\frac{1 - (80.5 Ne)}{f^{2}}]}^{1 / 2}$ where $n_{0} =$ that of free space. here, $N_{e}$ is electron - density which increases as these waves be deep into ionosphere. So correct option is (1).

PHXII08:ELECTROMAGNETIC WAVES

368902 Statement A :
One should not use metal containers in a microwave oven.
Statement B :
Only because metal may melt from heating.

1 Statement A is correct but Statement B is incorrect.

2 Statement A is incorrect but Statement B is correct.

3 Both statements are correct.

4 Both Statements are incorrect.

PHXII08:ELECTROMAGNETIC WAVES

368903 Assertion :
The television broadcasting becomes weaker with increasing distance.
Reason :
The power transmitted from $T V$ transmitter varies inversely as the distance of the receiver

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Power $\propto \frac{1}{r^{2}} (not \frac{1}{r})$
$T V$ signals weaken with distance following the inverse square law, diminishing in strength. As they spread over a larger area. additional transmitters or repeaters will be needed to extend coverage. So correct option is (3).

PHXII08:ELECTROMAGNETIC WAVES

368904 An antenna of length $25 m$ is mounted on top of a building of height $75 m$ . Then the maximum wavelength of the transmission signal is close to :

1

100 m

2

200 m

3

300 m

4

400 m

Explanation:

Length of antenna $\geq \frac{λ}{4}$
$∴ λ \leq 4 \times 25$
$\Rightarrow λ \leq 100 m .$

JEE - 2021

PHXII08:ELECTROMAGNETIC WAVES

368901 Assertion :
Propagation of electromagnetic waves (of $2 M H z$ to $30 M H z$ ) is done by Sky wave method.
Reason :
These waves are reflected back to earth by ionosphere.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Ionosphere her its refrective index $(n)$ given by $n = n_{o} {[\frac{1 - (80.5 Ne)}{f^{2}}]}^{1 / 2}$ where $n_{0} =$ that of free space. here, $N_{e}$ is electron - density which increases as these waves be deep into ionosphere. So correct option is (1).

PHXII08:ELECTROMAGNETIC WAVES

368902 Statement A :
One should not use metal containers in a microwave oven.
Statement B :
Only because metal may melt from heating.

1 Statement A is correct but Statement B is incorrect.

2 Statement A is incorrect but Statement B is correct.

3 Both statements are correct.

4 Both Statements are incorrect.

PHXII08:ELECTROMAGNETIC WAVES

368903 Assertion :
The television broadcasting becomes weaker with increasing distance.
Reason :
The power transmitted from $T V$ transmitter varies inversely as the distance of the receiver

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Power $\propto \frac{1}{r^{2}} (not \frac{1}{r})$
$T V$ signals weaken with distance following the inverse square law, diminishing in strength. As they spread over a larger area. additional transmitters or repeaters will be needed to extend coverage. So correct option is (3).

PHXII08:ELECTROMAGNETIC WAVES

368904 An antenna of length $25 m$ is mounted on top of a building of height $75 m$ . Then the maximum wavelength of the transmission signal is close to :

1

100 m

2

200 m

3

300 m

4

400 m

Explanation:

Length of antenna $\geq \frac{λ}{4}$
$∴ λ \leq 4 \times 25$
$\Rightarrow λ \leq 100 m .$

JEE - 2021

PHXII08:ELECTROMAGNETIC WAVES

368901 Assertion :
Propagation of electromagnetic waves (of $2 M H z$ to $30 M H z$ ) is done by Sky wave method.
Reason :
These waves are reflected back to earth by ionosphere.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Ionosphere her its refrective index $(n)$ given by $n = n_{o} {[\frac{1 - (80.5 Ne)}{f^{2}}]}^{1 / 2}$ where $n_{0} =$ that of free space. here, $N_{e}$ is electron - density which increases as these waves be deep into ionosphere. So correct option is (1).

PHXII08:ELECTROMAGNETIC WAVES

368902 Statement A :
One should not use metal containers in a microwave oven.
Statement B :
Only because metal may melt from heating.

1 Statement A is correct but Statement B is incorrect.

2 Statement A is incorrect but Statement B is correct.

3 Both statements are correct.

4 Both Statements are incorrect.

PHXII08:ELECTROMAGNETIC WAVES

368903 Assertion :
The television broadcasting becomes weaker with increasing distance.
Reason :
The power transmitted from $T V$ transmitter varies inversely as the distance of the receiver

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Power $\propto \frac{1}{r^{2}} (not \frac{1}{r})$
$T V$ signals weaken with distance following the inverse square law, diminishing in strength. As they spread over a larger area. additional transmitters or repeaters will be needed to extend coverage. So correct option is (3).

PHXII08:ELECTROMAGNETIC WAVES

368904 An antenna of length $25 m$ is mounted on top of a building of height $75 m$ . Then the maximum wavelength of the transmission signal is close to :

1

100 m

2

200 m

3

300 m

4

400 m

Explanation:

Length of antenna $\geq \frac{λ}{4}$
$∴ λ \leq 4 \times 25$
$\Rightarrow λ \leq 100 m .$

JEE - 2021

PHXII08:ELECTROMAGNETIC WAVES

368901 Assertion :
Propagation of electromagnetic waves (of $2 M H z$ to $30 M H z$ ) is done by Sky wave method.
Reason :
These waves are reflected back to earth by ionosphere.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Ionosphere her its refrective index $(n)$ given by $n = n_{o} {[\frac{1 - (80.5 Ne)}{f^{2}}]}^{1 / 2}$ where $n_{0} =$ that of free space. here, $N_{e}$ is electron - density which increases as these waves be deep into ionosphere. So correct option is (1).

PHXII08:ELECTROMAGNETIC WAVES

368902 Statement A :
One should not use metal containers in a microwave oven.
Statement B :
Only because metal may melt from heating.

1 Statement A is correct but Statement B is incorrect.

2 Statement A is incorrect but Statement B is correct.

3 Both statements are correct.

4 Both Statements are incorrect.

PHXII08:ELECTROMAGNETIC WAVES

368903 Assertion :
The television broadcasting becomes weaker with increasing distance.
Reason :
The power transmitted from $T V$ transmitter varies inversely as the distance of the receiver

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Power $\propto \frac{1}{r^{2}} (not \frac{1}{r})$
$T V$ signals weaken with distance following the inverse square law, diminishing in strength. As they spread over a larger area. additional transmitters or repeaters will be needed to extend coverage. So correct option is (3).

PHXII08:ELECTROMAGNETIC WAVES

368904 An antenna of length $25 m$ is mounted on top of a building of height $75 m$ . Then the maximum wavelength of the transmission signal is close to :

1

100 m

2

200 m

3

300 m

4

400 m

Explanation:

Length of antenna $\geq \frac{λ}{4}$
$∴ λ \leq 4 \times 25$
$\Rightarrow λ \leq 100 m .$

JEE - 2021