If a, b, c are in G.P., then
(a) a2, b2, c2 are in G.P. (b) a2(b+c),c2(a+b),b2(a+c) are in G.P. (c) a/(b+c), b/(c+a), c/(a+b) are in GP. (d)... View Article
Latest Posts
If Sn denotes the sum of first n terms of an A.P. whose first term is a and Snx/Sx is independent of x, then Sp =
(a) P3 (b) P2a (c) Pa2 (d) a3 Solution: Sum of n terms of AP = Sn = (n/2)[2a +... View Article
If [latex]S_{n}=(1+3^{-1})(1+3^{-2} )(1+3^{-4})(1+3^{-8})…(1+3^{-2^{n}})[/latex], then S∞ is equal to
(a) 1 (b) 1/2 (c) 3/2 (d) none Solution: Given \(\begin{array}{l}S_{n}=(1+3^{-1})(1+3^{-2} )(1+3^{-4})(1+3^{-8})…(1+3^{-2^{n}})\end{array} \) Multiply both sides by (1-3-1) (1-3-1)Sn =... View Article
The ratio of minimum to maximum wavelength in Balmer series is
1) 5 : 9 2) 5 : 36 3) 1 : 4 4) 3 : 4 Answer: 1) 5 : 9... View Article
The first excitation potential of a given atom is 10.2 V. Then, ionisation potential must be
1) 20.4 V 2) 13.6 V 3) 30.6 V 4) 40.8 V Answer: 2) 13.6 V Solution: First excitation potential of... View Article
The ratio of kinetic energy and the total energy of the electron in the nth quantum state of Bohr’s atomic model of hydrogen atom is
1) -2 2) -1 3) +2 4) +1 Answer: 2) -1 Solution: Kinetic energy K=(1/8πε0)⋅(Ze2/r) Total energy En=−(1/8πε0)⋅(Ze2/r) (K/En)=−1
Continuous emission spectrum is produced by
1) incandescent electric lamp 2) mercury vapour lamp 3) sodium vapour lamp 4) polyatomic substances Answer: 1) incandescent electric lamp Solution:... View Article
If an electron is revolving around the hydrogen nucleus at a distance of 0.1 nm, what should be its speed?
1) 2.188 × 106 ms-1 2) 1.094 × 106 ms-1 3) 4.376 × 106 ms-1 4) 1.59 × 106 ms-1... View Article
Which of the following transitions in Balmer series for hydrogen will have longest wavelength?
1) n = 2 to n = 1 2) n = 6 to n = 1 3) n = 3... View Article
The product of linear momentum and angular momentum of an electron of the hydrogen atom is proportional to nx, where x is
1) 0 2) 1 3) –2 4) 2 Answer: 1) 0 Solution: P x L ∝ nx Linear momentum, P = mv... View Article
The orbital frequency of an electron in the hydrogen atom is proportional to
1) n3 2) n-3 3) n 4) no Answer: 2) n-3 Solution: Time period, T = (4ε02n3h3)/Z2me4 T ∝ n3 Frequency, f =... View Article
If the electron in the hydrogen atom jumps from third orbit to second orbit the wavelength of the emitted radiation in term of Rydberg constant is
1) 6/5R 2) 36/5R 3) 64/7R 4) None of these Answer: 2) 36/5R Solution: Wavelength of emitted radiation is given by... View Article
In the hydrogen atom, an electron jumps from a bigger orbit to a smaller orbit so that radius of smaller orbit is one-fourth of radius of bigger orbit. If speed of electron in bigger orbit was v, then speed in smaller orbit is
1) v/4 2) v/2 3) v 4) 2v Answer: 4) 2v Solution: r ∝ n2rbig/rsmall =n2big/n2small =(4/1) ⇒nbig/nsmall =2 ⇒nsmall/nbig =1/2... View Article
Which of the following value is the correct order of nuclear density?
1) 5 × 105 kg/m3 2) 9 × 1010 kg/m3 3) 3 × 1021 kg/m3 4) 2 × 1017 kg/m3... View Article
An antenna is a device
1) That converts electromagnetic energy into radio frequency signal 2) That converts radio frequency signal into electromagnetic energy 3) That... View Article
An AM wave has 1800 watt of total power content. For 100% modulation the carrier should have power content equal to
1) 1000 watt 2) 1200 watt 3) 1500 watt 4) 1600 watt Answer: 2) 1200 watt Solution: Total power content, Pt... View Article
A silicon optical fibre has a core refractive index of 1.50 and a cladding refractive index of 1.47 what is the numerical aperture of the fibre?
1) 0.90 2) 0.60 3) 0.45 4) 0.30 Answer: 4) 0.30 Solution: Core refractive index, n1 = 1.50 Cladding refractive index,... View Article
In satellite communication 6 GHz frequency is used for ___________ and 4 GHz frequency is used for
1) Uplink, downlink 2) Downlink, uplink 3) Modulation, demodulation 4) Demodulation, modulation Answer: 1) Uplink, downlink Solution: In satellite communication, 6... View Article
Statement-1 :- Modulated wave is received directly on a headphone
Statement-2 :- High frequency waves are beyond audible range.
(a) Statement-1 is true, statement-2 is true. Statement-2 is a correct explanation for statement-1. (b) Statement-1 is true, statement-2 is... View Article
Statement-1:- Microwaves and not radio waves are used in satellite communication.
Statement-2:-The wavelength of microwaves is much shorter than that of radio waves. Hence microwaves do not disperse or diffract like radio waves.
(a) Statement-1 is true, statement-2 is true. Statement-2 is a correct explanation for statement-1. (b) Statement-1 is true, statement-2 is... View Article
