If the distance between two consecutive base pairs is 0.34 nm and the total number of base pairs of a DNA double helix in a typical mammalian cell is 6.6 × 10^9 bp, then the length of the DNA is approximately
a.
2.0 meters
b.
2.5 meters
c.
2.2 meters
Correct Answer
d.
2.7 meters
Step-by-Step AI Explanation
Verified Method
Length = 6.6 × 10^9 × 0.34 nm = 2.244 × 10^9 nm = 2.244 m, approximately 2.2 m.
Q97mcq
An element has a body-centered cubic (bcc) structure with a cell edge of 288 pm. The atomic radius is
a.
3/4 × 288 pm
Correct Answer
b.
2/4 × 288 pm
c.
4/3 × 288 pm
d.
4/2 × 288 pm
Step-by-Step AI Explanation
Verified Method
For bcc, 4r = √3 a, so r = (√3/4)a = (√3/4) × 288 pm.
Q103mcq
The calculated spin only magnetic moment of Cr2+ ion is
a.
3.87 BM
b.
4.90 BM
Correct Answer
c.
5.92 BM
d.
2.84 BM
Step-by-Step AI Explanation
Verified Method
Cr2+ is d4; spin-only magnetic moment μ = √n(n+2) with n = 4, giving 4.90 BM.
Q124mcq
The number of protons, neutrons and electrons in 17571Lu, respectively, are
a.
71, 104 and 71
Correct Answer
b.
104, 71 and 71
c.
71, 71 and 104
d.
175, 104 and 71
Step-by-Step AI Explanation
Verified Method
For 175Lu, atomic number Z = 71 gives 71 protons and 71 electrons; neutrons = 175 - 71 = 104.
Q136mcq
For which one of the following is Bohr model not valid?
a.
Hydrogen atom
b.
Singly ionised helium atom (He+)
c.
Deuteron atom
d.
Singly ionised neon atom (Ne+)
Correct Answer
Step-by-Step AI Explanation
Verified Method
Bohr model is valid for hydrogen-like species with one electron. Ne+ has more than one electron, so Bohr model does not apply.
Q136mcq
For which one of the following is Bohr model not valid?
a.
Hydrogen atom
b.
Singly ionised helium atom (He+)
c.
Deuteron atom
d.
Singly ionised neon atom (Ne+)
Correct Answer
Step-by-Step AI Explanation
Verified Method
Bohr model is applicable only to hydrogen-like species having one electron. Ne+ has more than one electron overall configuration complexity, so Bohr model is not valid.
Q137mcq
The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is: (c = speed of electromagnetic waves)
a.
c : 1
b.
1 : 1
Correct Answer
c.
1 : c
d.
1 : c2
Step-by-Step AI Explanation
Verified Method
In an electromagnetic wave, electric and magnetic fields contribute equally to the intensity; hence the ratio is 1:1.
Q137mcq
The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is (c = speed of electromagnetic waves):
a.
c : 1
b.
1 : 1
Correct Answer
c.
1 : c
d.
1 : c^2
Step-by-Step AI Explanation
Verified Method
In an electromagnetic wave, electric and magnetic fields contribute equally to the energy density and hence to intensity, so the ratio is 1:1.
Q138mcq
The Brewster's angle i_b for an interface should be
a.
0° < i_b < 30°
b.
30° < i_b < 45°
c.
45° < i_b < 90°
Correct Answer
d.
i_b = 90°
Step-by-Step AI Explanation
Verified Method
Since tan i_b = μ and for ordinary transparent media μ > 1, Brewster angle is greater than 45° and less than 90°.
Q139mcq
A cylinder contains hydrogen gas at pressure of 249 kPa and temperature 27°C. Its density is: (R = 8.3 J mol^-1 K^-1)
a.
0.5 kg/m^3
b.
0.2 kg/m^3
Correct Answer
c.
0.1 kg/m^3
d.
0.02 kg/m^3
Step-by-Step AI Explanation
Verified Method
Using ρ = PM/RT for hydrogen, ρ = (249000 × 2×10^-3)/(8.3 × 300) ≈ 0.2 kg/m^3.
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A ray is incident at an angle of incidence i on one surface of a small-angle prism (with angle of prism A) and emerges normally from the opposite surface. If the refractive index of the material of the prism is μ, then the angle of incidence is nearly equal to:
a.
A/(2μ)
b.
2A/μ
c.
μA
d.
A/(2μ) (repeated)
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Two cylinders A and B of equal capacity are connected to each other via a stop cock. A contains an ideal gas at standard temperature and pressure. B is completely evacuated. The entire system is thermally insulated. The stop cock is suddenly opened. The process is:
a.
isothermal
b.
adiabatic
c.
isochoric
d.
isobaric
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In a guitar, two strings A and B made of same material are slightly out of tune and produce beats of frequency 6 Hz. When tension in B is slightly decreased, the beat frequency increases to 7 Hz. If the frequency of A is 530 Hz, the original frequency of B will be:
a.
523 Hz
b.
524 Hz
c.
536 Hz
d.
537 Hz
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Two particles of mass 5 kg and 10 kg respectively are attached to the two ends of a rigid rod of length 1 m with negligible mass. The centre of mass of the system from the 5 kg particle is nearly at a distance of:
a.
33 cm
b.
50 cm
c.
67 cm
d.
80 cm
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Light with an average flux of 20 W/cm^2 falls on a non-reflecting surface at normal incidence having surface area 20 cm^2. The energy received by the surface during a time span of 1 minute is:
a.
10 × 10^3 J
b.
12 × 10^3 J
c.
24 × 10^3 J
d.
48 × 10^3 J
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A spherical conductor of radius 10 cm has a charge of 3.2 × 10^-7 C distributed uniformly. What is the magnitude of electric field at a point 15 cm from the centre of the sphere? (1/4πϵ0 = 9 × 10^9 N m^2 C^-2)
a.
1.28 × 10^4 N/C
b.
1.28 × 10^5 N/C
c.
1.28 × 10^6 N/C
d.
1.28 × 10^7 N/C
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A spherical conductor of radius 10 cm has a charge of 3.2 × 10^-7 C distributed uniformly. What is the magnitude of electric field at a point 15 cm from the centre of the sphere? [Take 1/(4πε0) = 9 × 10^9 N m^2 C^-2]
a.
1.28 × 10^4 N/C
b.
1.28 × 10^5 N/C
c.
1.28 × 10^6 N/C
d.
1.28 × 10^7 N/C
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In a certain region of space with volume 0.2 m^3, the electric potential is found to be 5 V throughout. The magnitude of electric field in this region is:
a.
zero
b.
0.5 N/C
c.
1 N/C
d.
5 N/C
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In a certain region of space with volume 0.2 m^3, the electric potential is found to be 5 V throughout. The magnitude of electric field in this region is:
a.
zero
b.
0.5 N/C
c.
1 N/C
d.
5 N/C
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Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current if the frequency is halved and intensity is doubled?
a.
doubled
b.
four times
c.
one-fourth
d.
zero
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Two bodies of mass 4 kg and 6 kg are tied to the ends of a massless string. The string passes over a pulley which is frictionless (see figure). The acceleration of the system in terms of acceleration due to gravity (g) is:
a.
g
b.
g/2
c.
g/5
d.
g/10
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A wire of length L, area of cross section A is hanging from a fixed support. The length of the wire changes to L1 when mass M is suspended from its free end. The expression for Young’s modulus is:
a.
MgL/(A L1)
b.
MgL/(A(L - L1))
c.
MgL1/(AL)
d.
MgL/(A(L1 - L))
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In Young’s double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes:
a.
double
b.
half
c.
four times
d.
one-fourth
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The capacitance of a parallel plate capacitor with air as medium is 6 μF. With the introduction of a dielectric medium, the capacitance becomes 30 μF. The permittivity of the medium is: (ε0 = 8.85 × 10^-12 C^2 N^-1 m^-2)
a.
0.44 × 10^-13 C^2 N^-1 m^-2
b.
1.77 × 10^-12 C^2 N^-1 m^-2
c.
0.44 × 10^-10 C^2 N^-1 m^-2
d.
5.00 C^2 N^-1 m^-2
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A series LCR circuit is connected to an ac voltage source. When L is removed from the circuit, the phase difference between current and voltage is π/3. If instead C is removed from the circuit, the phase difference is again π/3 between current and voltage. The power factor of the circuit is:
a.
zero
b.
0.5
c.
1.0
d.
-1.0
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A series LCR circuit is connected to an AC voltage source. When L is removed from the circuit, the phase difference between current and voltage is π/3. If instead C is removed from the circuit, the phase difference is again π/3 between current and voltage. The power factor of the circuit is:
a.
zero
b.
0.5
c.
1.0
d.
-1.0
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A short electric dipole has a dipole moment of 16 × 10^-9 C m. The electric potential due to the dipole at a point at a distance of 0.6 m from the centre of the dipole, situated on a line making an angle of 60° with the dipole axis is: (1/4πϵ0 = 9 × 10^9 N m^2/C^2)
a.
50 V
b.
200 V
c.
400 V
d.
zero
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An iron rod of susceptibility 599 is subjected to a magnetising field of 1200 A m^-1. The permeability of the material of the rod is (μ0 = 4π × 10^-7 T m A^-1).
a.
2.4π × 10^-4 T m A^-1
b.
8.0 × 10^-5 T m A^-1
c.
2.4π × 10^-5 T m A^-1
d.
2.4π × 10^-7 T m A^-1
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A long solenoid of 50 cm length having 100 turns carries a current of 2.5 A. The magnetic field at the centre of the solenoid is (μ0 = 4π × 10^-7 T m A^-1).
a.
6.28 × 10^-4 T
b.
3.14 × 10^-4 T
c.
6.28 × 10^-5 T
d.
3.14 × 10^-5 T
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An electron is accelerated from rest through a potential difference of V volt. If the de Broglie wavelength of the electron is 1.227 × 10^-2 nm, the potential difference is:
a.
10 V
b.
10^2 V
c.
10^3 V
d.
10^4 V
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A ball is thrown vertically downward with a velocity of 20 m/s from the top of a tower. It hits the ground after some time with a velocity of 80 m/s. The height of the tower is (g = 10 m/s^2):
a.
360 m
b.
340 m
c.
320 m
d.
300 m
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A capillary tube of radius r is immersed in water and water rises in it to a height h. The mass of the water in the capillary is 5 g. Another capillary tube of radius 2r is immersed in water. The mass of water that will rise in this tube is:
a.
2.5 g
b.
5.0 g
c.
10.0 g
d.
20.0 g
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A resistance wire connected in the left gap of a metre bridge balances a 10 Ω resistance in the right gap at a point which divides the bridge wire in the ratio 3:2. If the length of the resistance wire is 1.5 m, then the length of 1 Ω of the resistance wire is:
a.
1.0 × 10^-2 m
b.
1.0 × 10^-1 m
c.
1.5 × 10^-1 m
d.
1.5 × 10^-2 m
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