NEET IIT Modern Physics MCQ,NEET UG Practice Questions,PDFs,Quiz

# Modern Physics Mock Test-1

Question No:1
A ray of light of wavelength 5030A0 is incident on a totally reflecting surface. The momentum delivered by the ray is equal to
[A] 6.63 x10-27 kg-m/s
[B] 2.63 x10-27 kg-m/s
[C] 1.25 x10-24 kg-m/s
[D] None of the above

Question No:2
What is the binding energy per nucleon of 6C12 nucleus?
Given : Mass of C12 (mc) = 12.000u
Mass of proton (mp) = 1.0078u
Mass of neutron (mn) = 1.0087 u
And 1 amu= 931.4 $\frac{MeV}{C^2}$

[A] 5.26 MeV
[B] 6.2 MeV
[C] 4.65 MeV
[D] 7.68 MeV

Question No:3
Energy of 24.6 eV is required to remove one of the electrons from a neutral helium atom. The energy (in eV) required to remove both the electrons from a neutral helium atom is

[A] 38.2
[B] 49.2
[C] 51.8
[D] 79.0

Question No:4
If the radius of first Bohr’s orbit is “x”, then de-Broglie wavelength of electron in 3rd orbit is nearly

[A] 2πx
[B] 6πx
[C] 9x
[D] $\frac{X}{3}$

Question No:5
A star initially has 1040deuterons. It produces energy via the processes
12H +12H—–>12H +p and
12H+ 13H—–>24 He+n Where the masses of the nuclei are m(2H) =2.014amu, m(p) = 1.007 amu, m(n) = 1.008 amu and m((4(He) =4.001 amu, if the average power radiated by the star is 10(16W. The deuteron supply of the star is exhausted in a time of the order of

[A] 1018s
[C] 1012 s
[B] 1028s
[D] 1016s

Question No:6
Assuming that about 200 MeV energy is released per fission of 92 U235 nuclei. What would be the mass of U235 consumed per day in the fission of reactor of power 1 MW approximately?

[A] 10kg
[B] 1kg
[C] 1 g
[D] 10 g

Question No:7
The ratio between acceleration of the electron in singly ionized helium atom and doubly ionized lithium atom (both in ground state) is

[A] $\frac{4}{9}$

[B] $\frac{27}{8}$

[C]c) $\frac{8}{27}$

[D]d) $\frac{9}{4}$

Question No:8
A H-atom moving with speed v makes a head on collision with a H-atom at rest. Both atoms are in ground state. The minimum value of velocity v for which one of the atom may excite is
[A] 6.25 x 104 m/s
[B] 8 x 104 m/s
[C] 7.25 x 104 m/s
[D] 13.6 x 104 m/s
Note : mH = 1.67 x 10-27 kg

Question No:9
In the reaction12H+ 23H——>24He+01n, if the binding energies per nucleon of 12H, 13 H and24He, are x, y and z respectively. Then energy released in the process is

[A] 2x + 3y – 4z
[B] 4z – 2x – 3y
[C] Zx + 3y – 5z
[D] None of these

Question No:10
In Moseley’s equation,$\sqrt{ v} = a( Z — b)$ , for X-rays

[A] a is independent but b depends on target material
[B] both a and b are independent of the target material
[C] both a and b depend on the target material
[D] b is independent but a depends on the target material

Question No:11
. The activity of a sample of radioactive material is A1 at time t1 and A2 at time t2 (t2 > t1). Its mean life is T. Then

[A] A1t1 = A2t2
[B]$\frac{A_1-A_2}{t_2-t_1}$ = constant
[C] A2=A1e$\frac{(t_1-t_2)}{T}$

None of these

Question No:12
A particular nucleus in a large population of identical radioactive nuclei did survive 5 half lifes of that isotope. Then the probability that this surviving nucleus will survive the next half-life is
[A]$\frac{1}{32}$

[B] $\frac{1}{5}$

[C] $\frac{1}{2}$

[D] $\frac{1}{10}$

Question No:13
Two electrons are moving with the same speed v. One electron enters a region of uniform electric field while the other enters a region of uniform magnetic field. Then after some time if the de-Broglie wavelengths of the two are λ1 and λ1 then
[A] λ12
[B] λ1 > λ1
[C] λ1 < λ2
[D] λ12 or λ12

Question No:14
A stationary radioactive nucleus of mass 210 units disintegrates into an alpha particle of mass 4 units and residual nucleus of mass 206 units. If the kinetic energy of the alpha particle is E, the kinetic energy of the residual nucleus is

[A] $\frac{2}{105}$

[B]$\frac{2}{103}$

[C]$\frac{103}{2}$

[D]$\frac{105}{2}$

Question No:15
The magnetic field at the centre of a hydrogen atom due to the motion of the electron in the first Bohr orbit is B. The magnetic field at the centre due to the motion of the electron in the second Bohr orbit will be

[A] $\frac{B}{4}$

[B] $\frac{B}{8}$

[C] $\frac{B}{32}$

[D] $\frac{B}{64}$

Question No:16
An excited hydrogen atom emits a photon of wavelength K in returning to the ground state. The quantum number n of the excited state is given by (R = Rydberg constant)

[A] $\sqrt{λR(λR-1) }$

[B] $\sqrt\frac{λR}{(λR-1) }$

[C] $\sqrt\frac{(λR-1) }{λR}$

[D] $\sqrt\frac{1}{λR(λR-1) }$

Question No:17
17. Magnetic moment of an electron in nth orbit of hydrogen atom is

[A]$\frac{neh}{πm}$

[B]$\frac{neh}{4πm}$

[C] $\frac{meh}{4πn}$

[D]$\frac{meh}{4πn}$
[m = mass of electron, h = Planck’s constant]

Question No:18
The probability of survival of a radioactive nucleus for one mean life is

[A]$\frac{1}{e}$

[B]$(1-\frac{1}{e})$

[C]$\frac{ln2}{e}$

[D]$1- \frac{ln2}{e} )$

Question No:19
When the voltage applied to an X-ray tube is increased from V1 = 1 0 kV to V2 =20 kV, the wavelength difference between the Kα line and the short wavelength limit of the continuous X-ray spectrum increases by a factor 3. The atomic number of the element of which the tube anticathode is made will be

[A] 62
[B] 56
[C] 45
[D] 29

Question No:20
Light of wavelength 330 nm falling on a piece of metal ejects electrons with sufficient energy with requires voltage V0 to prevent them from reaching a collector. In the same setup, light of wavelength 220 nm, ejects electrons which require twice the voltage V0 to stop them in reaching a collector. The numerical value of voltage V0 is

[A] $\frac{16}{15}$V
[B] $\frac{15}{16}$V
[C] $\frac{15}{8}$V
[D] $\frac{8}{15}$V

Question No:21
Maximum KE of a photoelectron is E when the wavelength of incident light is λ If energy becomes four times when wavelength is reduced to one-third, then work function of the metal is

[A]$\frac{3hc}{λ}$

[B]$\frac{hc}{3λ}$

[C]$\frac{hc}{λ}$

[D]$\frac{hc}{2λ}$

Question No:22
If the frequency of Kα X-ray emitted from the element with atomic number 31 is “f”, then the frequency of Kα X-ray emitted from the element with atomic number 51 would be

[A] $\frac{5f}{3}$

[B] $\frac{51f}{31}$

[C] $\frac{9f}{25}$

[D] $\frac{25f}{9}$