Archives

The characteristics impedance of a coaxial cable of the order of

1) 50 Ω 2) 200 Ω 3) 27 Ω 4) None of these Answer: 1) 50 Ω Solution: The characteristics impedance of a... View Article

Suppose the sun was located at the position occupied by the nearest star, say, alphacenturi 4 light years away. By what factor the solar radiation received per sec per unit area decrease

1) 1.5 × 10–6 2) 1.5 × 10–8 3) 1.5 × 10–9 4) 1.5 ×10–11 Answer: 4) 1.5... View Article

Assertion Diode lasers are used as optical sources in optical communication.

Reason Diode lasers consume less energy.

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... View Article

Statement I Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals.

Statement II The state of ionosphere varies from hour to hour, day to day and season to season

1) Statement I is true, statement II is true; statement II is a correct explanation for statement I 2) Statement I is true, statement II is... View Article

An amplitude modulated wave is modulated to 50%. What is the saving in power if carrier as well as one of the side bands are suppressed?

1) 70% 2) 65.4% 3) 94.4% 4) 25.5% Answer:3) 94.4% Solution: Psb = Pc(ma/2)2 = Pc(0.5)2/4 = 0.0625 Pc Also ... View Article

The maximum range, dmax, of radar is

1) Proportional to the cube root of the peak transmitted power 2) Proportional to the fourth root of the peak transmitted power 3)... View Article

A photodetector is made from a semiconductor with Eg = 0.73 eV. What is the maximum wavelength, which it can detect?

1) 1000 nm 2) 1703 nm 3) 500 nm 4) 173 nm Answer: 2) 1703 nm Solution: The energy of photon above the bandgap energy is... View Article

Radar has a power of 1 kW and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500 m. The maximum distance up to which it can detect objects located on the surface of the earth (Radius of earth = 6.4 x 10⁶m) is

1) 80 km 2) 16 km 3) 40 km 4) 64 km Answer: 1) 80 km Solution: Let d be the maximum distance at which the object can be detected... View Article

Phase difference between space current and capacitive current is

1) π rad 2) π/2 rad 3) 3π/2 rad 4) μ rad Answer: 1) π rad Solution: The phase difference between space current and... View Article

What is the velocity of electromagnetic waves in a good conductor

1) 3 x 108 m/s 2) More than 3 x 108 m/s 3) High 4) Very low Answer: 4) Very low Solution: The velocity of electromagnetic waves in a... View Article

How long will it take to transmit the information 30 km away in space?

1) 0.1 m s 2) 0.1 µ s 3) 0.1 n s 4) 0.1 p s Answer: 1) 0.1 m s Solution: Velocity of light in space,= [(distance... View Article

When electromagnetic waves enter the ionised layer of the ionosphere, the relative permitting of the ionised layer

1) Remain constant 2) Appears to decrease 3) Appears to increase 4) Changer randomly Answers: 2) Appears to decrease Solution:... View Article

For 100% modulation, What is the value of minimum amplitude ( E_min ) of the modulated wave?

1) Zero 2) 1 3) 2 4) 3 Answer: 1) Zero Solution: m = [(Emax – Emin) / (Emax + Emin)] × 100 For m = 100%, Emin should be zero.... View Article

A silicon optical fibre with a core diameter large enough has a care refractive index of 1.50 and a cladding refractive index of 1.47. The critical angle at the core-cladding interface is ___________

1) 87.50 2) 78.50 3) 38.50 4) 450 Answer: n1 = core refractive index = 1.5 n2 = cladding refractive index = 1.47 Critical angle θ = sin–1... View Article

What type of medium is used in optical communication?

1) Guided medium 2) Unguided medium 3) Both guided and unguided media 4) Neither guided nor unguided media Answer: 1) Guided medium... View Article

What is the frequency range of signals that can be transmitted in the care of twisted pair of wires?

1) 5 MHz to 20 MHz 2) 5 MHz to 10 MHz 3) 100 Hz to 4 MHz 4) 5 MHz to 20 MHz Answer: 3) 100 Hz to 4 MHz Solution: The frequency... View Article

A T.V. tower has a height of 200 m. By how much the height of the tower is increased to triple its coverage range?

1) 1600 m 2) 800 m 3) 1800 m 4) 600 m Answer: 1) 1600 m Solution: Here, h=200m,as d=√2hr and d'=√2h'R d'=3d... View Article

In order to cover a circular region of radius 128 km by a TV transmitter, what must be the height of the transmitting antenna?

1) 79 m 2) 1050 m 3) 1280 m 4) 1560 m Answer: 3) 1280 m Solution: Area of circular region = πR2 = 3.14 × (128)2 =... View Article

A rod AB of length 16 cm rests between the wall AD and a smooth peg, 1 cm from the wall, and makes an angle θ with the horizontal. The value of θ for which the height of G, the midpoint of the rod above the peg is minimum, is

(a) 150 (b) 300 (c) 600 (d) 750 Solution: We have AC = sec θ, AG = 8 CG = 8 - sec θ (C being the peg). u = CG sin θ = (8 - sec θ) sin θ... View Article

The difference between greatest and least value of f(x) = 2 sin x + sin 2x, x ∈ [0, 3π/2] is

(a) 3√3/2 (b) 3√3/2 - 2 (c) (3√3/2) + 2 (d) none of these Solution: f(x) = 2 sin x + sin 2x Differentiate w.r.t.x... View Article