CBSE
The binding energy per nucleon of deuteron (^{2}_{1}H) and helium nucleus (^{4}_{2}He) is 1.1 MeV and 7 MeV respectively. If two deuteron nuclei react to form a single helium nucleus, then the energy released is
13.9 MeV
26.9 MeV
23.6 MeV
19.2 MeV
C.
23.6 MeV
As given,
The binding energy per nucleon of a deuteron (_{1}H^{2} ) = 1.1 MeV
∴ Total binding energy = 2× 1.1 = 2.2 MeV
The binding energy per nucleon of helium (_{2}He^{4} ) = 7 MeV
∴ Total binding energy = 4× 7 = 28 MeV
Hence, energy released in the above process = 28 - 2× 2.2 = 28 - 4.4 = 23.6 MeV
According to Einstein’s photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal Vs the frequency, of the incident radiation gives straight line whose slope
depends on the nature of the metal used
depends on the intensity of the radiation
depends both on the intensity of the radiation and the metal used
is the same for all metals and independent of the intensity of the radiation.
D.
is the same for all metals and independent of the intensity of the radiation.
Two spherical conductor B and C having equal radii and carrying equal charges in them repel each other with a force F when kept apart at some distance. A third spherical conductor having same radius as that of B but uncharged brought in contact with B, then brought in contact with C and finally removed away from both. The new force of repulsion, between B and C is
F/4
3F/4
3F/8
F/8
C.
3F/8
The angle of incidence at which reflected light totally polarized for reflection from air to glass (refractive index n), is
sin^{−1} (n
sin^{−1} (1/n)
tan^{−1} (1/n)
tan^{−1} (n)
D.
tan^{−1} (n)
Brewster’s law: According to this law the ordinary light is completely polarised in the plane of incidence when it gets reflected from transparent medium at a particular angle known as the angle of polarisation. n = tan ip.
An electromagnetic wave of frequency ν = 3.0 MHz passes from vacuum into a dielectric medium with permittivity ε = 4.0. Then
wavelength is doubled and the frequency remains unchanged
wavelength is doubled and frequency becomes half
wavelength is halved and frequency remains unchanged
wavelength and frequency both remain unchanged.
C.
wavelength is halved and frequency remains unchanged
In vacuum, ε0 = 1
In medium, ε = 4
So, refractive index
Hence, it is clear that wavelength and velocity will become half but frequency remains unchanged when the wave is passing through any medium.
An α-particle of energy 5 MeV is scattered through 180° by a fixed uranium nucleus. The distance of the closest approach is of the order of
1 Å
10^{−10} cm
10^{−12} cm
10^{−15} cm
C.
10^{−12} cm
At closest approach, all the kinetic energy of the α-particle will converted into the potential energy of the system, K.E. = P.E.
A nucleus disintegrates into two nuclear parts which have their velocities in the ratio 2:1. The ratio of their nuclear sizes will be
2^{1/3}:1
1:3^{1/2}
3^{1/2}:1
1:2^{1/3}
B.
1:3^{1/2}
Law of conservation of momentum gives
m_{1} v_{1} = m_{2} v_{2}
The work function of a substance is 4.0 eV. Then longest wavelength of light that can cause photoelectron emission from this substance approximately
540 nm
400 nm
310 nm,
220 nm
C.
310 nm,
The thermistors are usually made of
metals with low temperature coefficient of resistivity
metals with high temperature coefficient of resistivity
metal oxides with high temperature coefficient of resistivity ‘
semiconducting materials having low temperature coefficient of resistivity.
C.
metal oxides with high temperature coefficient of resistivity ‘
These are devices whose resistance varies quite markedly with temperature mean having high-temperature coefficient of resistivity. [Their name are derived from thermal resistors]. Depending on their composition they can have either negative temperature coefficient or positive temperature coefficient or positive temperature coefficient or positive temperature coefficient characteristics. The negative temperature coefficient types consist of a mixture of oxides of iron, nickel and cobalt with small amounts of other substance. The positive temperature coefficient types are based on barium titanate.
The maximum number of possible interference maxima for slit-separation equal to twice the wavelength in Young’s double-slit experiment is
infinite
five
three
zero
B.
five
For interference maxima, d sin θ = nλ Here d = 2λ
∴ sin θ = n/2 and is satisfied by 5 integral values of n (−2, −1, 0, 1, 2), as the maximum value of sin θ can only be 1.