Propagation of Waves

Q. if a star is moving towards the earth with a relative velocity of 0.8c.Then what is the frequency of the light observedby the observer on the earth if it emits light of 6000 hz. and what will be the frequency observed if the star moves away from eart

Q. The impedance of coaxial cable, when its inductance is 0.40 $\mu$H and capacitance is 1 $\times {10}^{-11}$ F, can be

1. 2 $\times {10}^2\Omega$
2. 100 $\Omega$
3. 3 $\times {10}^3\Omega$
4. 3 $\times {10}^{-2}\Omega$

Q. For the given uniformly charged ring of linear charge density $+10\text{nC/m}$, the electric field in $y-$ direction at point $\text{P}$ is

1. $200\text{N/C}$
2. $150\text{N/C}$
3. Zero
4. $100\text{N/C}$

Q.

In which frequency range, space waves are normally propagated

1. HF

2. VHF

3. UHF

4. SHF

Q. Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : Television signals are received through sky-wave propagation.
Reason : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.

1. If both assertion and reason are true and the reason is the correct explanation of the assertion.
2. If both assertion and reason are true but reason is not the correct explanation of the assertion.
3. If assertion is true but reason is false.
4. If the assertion and reason both are false.
5. If assertion is false but reason is true.

Q. Consider an optical communication system operating at l~800 nm. Suppose, only 1% of the optical source frequency is the available channel bandwidth for optical communication. How many channels can be accommodated for transmitting audio signals requiring a bandwidth of 8 kHz

1. 4.8 $\times {10}^8$
2. 48
3. 6.2 $\times {10}^8$
4. 4.8 $\times {10}^5$

Q. Consider telecommunication through optical fibers. Which of the following statements is not true

1. Optical fibers may have homogeneous core with a suitable cladding
2. Optical fibers can be of graded refractive index
3. Optical fibers are subject to electromagnetic interference from outside
4. Optical fibers have extremely low transmission loss

Q. Consider telecommunication through optical fibres. Which of the following statements is not true.

1. Optical fibres may have homogeneous core with a suitable cladding.
2. Optical fibres are subject to electromagnetic interference from outside.
3. Optical fibres can be of graded refractive index
4. Optical fibres have extremely low transmission loss

Q. In which of the following remote sensing technique is not used

1. Forest density
2. Pollution
3. Wetland mapping
4. Medical treatment

Q. Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion: Short wave bands are used for transmission of radio waves to a large distance.
Reason : Short waves are reflected by ionosphere
(a)If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b)If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c)If assertion is true but reason is false.
(d)If the assertion and reason both are false.
(e)If assertion is false but reason is true.

1. a
2. b
3. c
4. d
5. e

Q. A ground receiver station is receiving a signal at (i) 5 MHz and transmitted from a ground transmitter at a height of 300 m, located at a distance of 100 km from the receiver station. The signal is coming via__________. Radius of earth = 6.4 $\times {10}^6$m. $N_{max}$ of isosphere = ${10}^{12}{m}^3$

1. Space wave
2. Sky wave propagation
3. Satellite transponder
4. All of these

Q. Through which mode of propagation, the radio waves can be sent from one place to another

1. Ground wave propagation
2. Sky wave propagation
3. Space wave propagation
4. All of them

Q. A sky wave with a frequency 55 MHz is incident on D-region of earth's atmosphere at ${45}^{\circ }$. The angle of refraction is (electron density for D-region is 400 electron/${cm}^3$)

1. ${60}^{\circ }$
2. ${45}^{\circ }$
3. ${30}^{\circ }$
4. ${15}^{\circ }$

Q. Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion :The electromagnetic waves of shorter wavelength can travel longer distances on earth's surface than those of longer wavelengths.
Reason : Shorter the wavelength, the larger is the velocity of wave propagation.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. The assertion and reason both are false.

Q. Figure shown two coherent sources S₁ and S₂ which emit sound of wavelength λ in phase. The separation between the sources is 3λ. A circular wire of large radius is placed in such way that S₁, S₂ is at the centre of the wire. Find the angular positions θ on the wire for which constructive interference takes place.

Q. Mean optical power launched into an 8 km fiber is 120 $\mu$W and mean output power is 4 $\mu$W, then the overall attenuation is (Given log 30 = 1.477)

1. 14.77 dB
2. 16.77 dB
3. 3.01 dB
4. None of these

Q. Mean optical power launched into an 8 km fiber is 120 $\mu$W and mean output power is 4 $\mu$W, then the overall attenuation is (Given log 30 = 1.477)

1. 14.77 dB
2. 16.77 dB
3. 3.01 dB
4. None of these

Q. Diagram hertz atmospher and define sky wave propagation