Question 2 :
The number of neutrons in a chain reaction increases in -

Question 3 :
The graph between the stopping potential V₀ and frequency (n) of incident photons for photocell is a straight line with a slope -

Question 4 :
The kinetic energy of most energetic electrons emitted from a metallic surface is doubled when the wavelength λ of the incident radiation is changed from 400 nm to 310 nm. The work function of the metal is-

Question 6 :
When ₉₂U²³⁵ undergoes fission, 0.1% of its original mass is changed into energy. How much energy is released if 1 kg of ₉₂U²³⁵undergoes fission?

Question 8 :
An X-ray tube is operated at a constant potential difference and it is required to get X-rays of wavelength not less than 0.2 nm. Then the potential difference in kilovolt is<br>[Given : h = 6.63 &times; 10^-34 J s, e = 1.6 &times; 10^-19 c, <br>c = 3 &times; 10⁸ m s^-1]

Question 9 :
The energy released per fission of uranium-235 is about 200 MeV. A reactor using U-235 as fuel is producing 1000 kilowatts power. The number of U-235 nuclei undergoing fission per second is, approximately-

Question 10 :
In an experiment tungsten cathode which has a threshold wavelength 2300 &#8491; is irradiated by ultraviolet light of wavelength 1800 &#8491;. The maximum energy of emitted photo-electron will be -

Question 11 :
&mu;-meson is a particle which has charge same as that of the electron and mass 207 times the mass of electron. A &mu;-mesonic atom is formed when a &mu;-meason is captured by proton. The ionization energy of such an atom is-

Question 12 :
If a source of power {tex} 4 \mathrm { kW } {/tex} produces {tex} 10 ^ { 20 } {/tex} photons/second, the radiation belongs to a part of the spectrum called

Question 13 :
1 g of hydrogen is converted into 0.993 g of helium in a thermonuclear reaction. The energy released is

Question 14 :
The masses of two radioactive substances are same and their half-lives are 1 year and 2 years respectively. The ratio of their activities after six years will be-

Question 15 :
At any instant the ratio of the amount of radioactive substances is 2 : 1. If their half lives be respectively 12 and 16 hours, then after two days, what will be the ratio of the substances

Question 16 :
The count rate of a Geiger-Muller counter for the radiation of radioactive material of half life of 30 minutes decreases to 5 s^-1 after 2 hours. The initial count rate was -

Question 17 :
Above graph shows stopping potential versus <img style='object-fit:contain' src='https://storage.googleapis.com/teachmint/question_assets/JEE%20Main/5e7885e8135d6370e9dc1ac8' height='37' width='69' >for three metals, then -<br><img style='object-fit:contain' src='https://storage.googleapis.com/teachmint/question_assets/JEE%20Main/5e7885e88ad4296d0cdf896f' height='126' width='240' >

Question 18 :
Two alpha-particles with equal energies are fired towards the nucleus of a gold atom. Which diagram could represent their paths (in the plane of the paper)?<br><img style='object-fit:contain' src='https://storage.googleapis.com/teachmint/question_assets/JEE%20Main/5e788432135d6370e9dc19ab' height='209' width='325' >

Question 19 :
Consider the nuclear reaction X²⁰⁰&rarr; A ¹¹⁰ + B⁸⁰. If the binding energy per nucleon for X, A and B are 7.4 MeV, 8.2 MeV and 8.1 MeV respectively, then the energy released in the reaction -

Question 20 :
₈₆A²²²&rarr;₈₄B²¹⁰. In this reaction how many &alpha; and &beta; particles are emitted -

Question 21 :
<font>In an experiment tungsten cathode which has a threshold wavelength 2300 Å is irradiated by ultraviolet light of wavelength 1800 Å. The maximum energy of emitted photo-electron will be -</font></p>

Question 22 :
<font>What is the force exerted by a photon of intensity 1.4 kWm</font>^{<font>-2</font>}<font> if it falls on a perfect absorber of radius 2 metre ?</font></p>

Question 23 :
<font>In the davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased</font></p>

Question 24 :
<font>If the momentum of an electron is changed by p, then the de Broglie wavelength associated with it changes by 0.5% . The initial momentum of electron will be:</font></p>

Question 25 :
<font>Which of the following statement is correct regarding the photoelectric experiment?</font></p>