### Mordern Physics

74. A nucleus reactor has a power of 16 kW if the energy per fission is 200 MeV then number of fissions per second is **[2075]**

5 x 10^{17}

5 x 10^{16}

5 x 10^{15}

5 x 10^{14}

75. To obtain p-type silicon semiconductor, pure silicon may be doped with **[2075]**

Aluminum

Oxygen

phosphorous

copper

74. According to Bohr's model of the H-atom, the radius of stationary orbit characterized by the principle of quantum number n is proportional to **[2074]**

π / n

n^{2}

n

1/n^{2}

69. The photoelectric is based on the law of conservation of. **[2073]**

energy

mass

momentum

angular momentum of photons

70. When a radioactive element emits a β-particle the mass number of the atom **[2073]**

increase by one

decreases by one

remains the same

decreases by four

75. In which region of electromagnetic spectrum does the layman series of atom Lie?**[2073]**

Ultraviolet

visible

infrared

microwave

71. The ratio of specific charge of proton to that of an alpha particle is **[2072]**

1:4

1:2

4:1

2:1

73. The approximate radius of aluminum nucleus is **[2072]**

1.5 Fermi

2.5 Fermi

4.5 Fermi

13.5 Fermi

74. The kinetic energy of a particle is doubled, de Broglie wavelength becomes **[2072]**

2 times

4 times

2 times

1/2 times

75. Half life and mean life of a radioactive element are related. Choose correct answer from the following **[2072]**

Half life is less than the mean life

Half life is more than the mean life

mean life and the half life are the same

mean life is exactly two times the half life

72. The angular momentum of electron in the hydrogen atom in the ground state is **[2071]**

h/2π

h/4π

h2

2h

73. The approximate radius of aluminum nucleus is **[2071]**

1.5 Fermi

2.5 Fermi

4.5 Fermi

13.5 Fermi

74. The kinetic energy of a particle is doubled, de Broglie wavelength becomes **[2071]**

2 times

4 times

2 times

1/2 times

75. Half life and mean life of a radioactive element are related. Choose correct answer from the following **[2071]**

Half life is less than the mean life

Half life is more than the mean life

mean life and the half life are the same

mean life is exactly two times the half life

72. Electron in the atom are held due to **[2071]**

Nuclear forces

Coulomb forces

Van der Waals force

Gravitational forces

73. Which series of H atom lies in visible region?**[2071]**

Lyman

Bracket and Paschen

Balmer

Paschen

74. The half-life of a substance is 1600 years. The mean life is **[2071]**

1600 yrs

3200 yrs

800 yrs

2309 yrs

75. Rydberg constant is **[2071]**

Same for all element

Different for different element

A universal constant

Is diffrent for lighter element but same for heavier elements

69. A particle of mass 10^{-31} kg is moving with a speed of 10^{5}m/s. The De-Broglie wavelength of the particle is ...... **[2070]**

6.63 x 10^{-8} m

6.63 Å

66.3 Å

6.63 x 10^{-7}m

71. Hard X-rays are compared to soft X-rays have**[2070]**

Higher Intensity

Lower frequency

Higher Frequency

Higher Speed

72. The mass of α-particle is **[2070]**

Equal to the mass of four protons

Equal to the mass of four neutrons

Equal to the masses of 2 protons and 2 neutrons

Less than the sum of masses of 2 protons and 2 neutrons