The waves used in telecommunication are

(1) infrared

(2) visible light

(3) microwaves

(4) ultraviolet rays

The frequency \(1057~\text{MHz}\) of radiation arising due to electron transition between two close energy levels in hydrogen belongs to:
1. radio waves
2. infrared waves
3. microwaves
4. \(\gamma\text-\)rays

The shortest wavelength of X-rays emitted from an X-ray tube depends upon

(1) nature of the gas in the tube

(2) the voltage applied to the tube

(3) current in the tube

(4) nature of the target of the tube

X-rays are not used for radar purposes, because they are not 

(1) reflected by target

(2) partly absorbed by the target

(3) electromagnetic waves

(4) completely absorbed by the target

The energy of the X-rays photon is 3.3$\times {10}^{-16}$J. Its frequency is :

(1) $2\times {10}^{19} Hz$

(2) $5\times {10}^{18} Hz$

(3) $5\times {10}^{17} Hz$

(4) $5\times {10}^{16} Hz$

A plane electromagnetic wave

$E_z=100 \cos (6\times {10}^{8}t+4x) V/m$

propagates in a medium of dielectric constant

(1) 1.5

(2) 2.0

(3) 2.4

(4) 4.0

The magnetic field between the plates of radius 12 cm separated by a distance of 4 mm of a parallel plate capacitor of capacitance 100 pF along the axis of plates having conduction current of 0.15 A is

(1) zero

(2) 1.5 T

(3) 15 T

(4) 0.15 T

A larger parallel plate capacitor, whose plates have an area of \(1~\text{m}^2,\) separated from each other by \(1\) mm, is being charged at a rate of \(25.8\) V/s. If the plates have dielectric constant \(10\), then the displacement current at this instant is:
1. \(25~\mu\text{A}\)
2. \(11~\mu\text{A}\)
3. \(2.2~\mu\text{A}\)
4. \(1.1~\mu\text{A}\)

A parallel plate capacitor with plate area \(A\) and separation between the plates \(d\), is charged by a source having current \(i\) at some instant. Consider a plane surface of area \(A/2\) parallel to the plates and drawn symmetrically between the plates. The displacement current through this area is:
1. \(i\) 
2. \(i/2\) 
3. \(i/4\) 
4. \(i/8\)

The sun delivers \(10^{3}~\text{W/m}^2\) of electromagnetic flux to the earth's surface. The total power that is incident on a roof of dimensions \(8\) m$\times$\(20\) m will be:
1. \(2.56\times 10^{4}~\text{W}\)
2. \(6.4\times 10^{5}~\text{W}\)
3. \(4.0\times 10^{5}~\text{W}\)
4. \(1.6\times 10^{5}~\text{W}\)