Physics M.C.Q (1 Marks)

Laser beams are used to measure long distances because

(a) They are monochromatic	(b) They are highly polarised
(c) They are coherent	(d) They have high degree of parallelism

A laser beam is used for carrying out surgery because it

(a) Is highly monochromatic	(b) Is highly coherent
(c) Is highly directional	(d) Can be sharply focussed

The maximum distance upto which TV transmission from a TV tower of height h can be received is proportional to

(a) h1/2

(b) h

(c) h3/2

(d) h2

The attenuation in optical fibre is mainly due to

(a) Absorption	(b) Scattering
(c) Neither absorption nor scattering	(d) Both (a) and (b)

The electromagnetic waves of frequency 2 MHz to 30 MHz are

(a) In ground wave propagation	(b) In sky wave propagation
(c) In microwave propagation	(d) In satellite communication

Maximum useable frequency (MUF) in F-region layer is x, when the critical frequency is 60 MHz and the angle of incidence is 70°. Then x is

(a) 150 MHz

(b) 170 MHz

(c) 175 MHz

(d) 190 MHz

An antenna behaves as resonant circuit only when its length is

(a)	(b)
(c)	(d)  or integral multiple of

Broadcasting antennas are generally

(a) Omnidirectional type

(b) Vertical type

(c) Horizontal type

(d) None of these

The carrier frequency generated by a tank circuit containing 1 nF capacitor and 10 mH inductor is

(a) 1592 Hz

(b) 1592 MHz

(c) 1592 kHz

(d) 159.2 Hz

A laser beam of pulse power 10¹² watt is focussed on an object are 10^–4 cm². The energy flux in watt/ cm² at the point of focus is

(a) 1020

(b) 1016

(c) 108

(d) 104

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

(a) Ground wave propagation	(b) Sky wave propagation
(c) Space wave propagation	(d) All of them

In which frequency range, space waves are normally propagated

(a) HF

(b) VHF

(c) UHF

(d) SHF

The characteristic impedance of a coaxial cable is of the order of

(a) 50 W

(b) 200 W

(c) 270 W

(d) None of these

A step index fibre has a relative refractive index of 0.88%. What is the critical angle at the corecladding interface

(a) 60°

(b) 75°

(c) 45°

(d) None of these

Long distance short-wave radio broadcasting uses

(a) Ground wave

(b) Ionospheric wave

(c) Direct wave

(d) Sky wave

The process of superimposing signal frequency (i.e. audio wave) on the carrier wave is known as

(a) Transmission

(b) Reception

(c) Modulation

(d) Detection

In short wave communication waves of which of the following frequencies will be reflected back by the ionospheric layer, having electron density 10¹¹ per m³

(a) 2 MHz

(b) 10 MHz

(c) 12 MHz

(d) 18 MHz

In an amplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frequency will be

(a) 50 cycles/sec

(b) 100 cycles/sec

(c) 500 cycles/sec

(d) 50,000 cycles/sec

AM is used for broadcasting because

(a) It is more noise immune than other modulation systems

(b) It requires less transmitting power compared with other systems

(c) Its use avoids receiver complexity

(d) No other modulation system can provide the necessary bandwidth faithful transmission

Range of frequencies allotted for commercial FM radio broadcast is

(a) 88 to 108 MHz

(b) 88 to 108 kHz

(c) 8 to 88 MHz

(d) 88 to 108 GHz

The velocity factor of a transmission line x. If dielectric constant of the medium is 2.6, the value of x is

(a) 0.26

(b) 0.62

(c) 2.6

(d) 6.2