JEE Main 2020 (Online) 3rd September Morning Slot | Atoms and Nuclei Question 115 | Physics

JEE Main 2020 (Online) 3rd September Morning Slot

MCQ (Single Correct Answer)

-1

In a radioactive material, fraction of active material remaining after time t is 9/16. The fraction that was remaining after t/2 is

$${3 \over 4}$$

$${4 \over 5}$$

$${3 \over 5}$$

$${7 \over 8}$$

JEE Main 2020 (Online) 2nd September Evening Slot

MCQ (Single Correct Answer)

-1

In a hydrogen atom the electron makes a transition from (n + 1)^th level to the n^th level. If n >> 1, the frequency of radiation emitted is proportional to :

$${1 \over n}$$

$${1 \over {{n^2}}}$$

$${1 \over {{n^3}}}$$

$${1 \over {{n^4}}}$$

JEE Main 2020 (Online) 2nd September Morning Slot

MCQ (Single Correct Answer)

-1

In a reactor, 2 kg of ₉₂U²³⁵ fuel is fully used up in 30 days. The energy released per fission is 200 MeV. Given that the Avogadro number, N = 6.023 $$ \times $$ 10²⁶ per kilo mole and 1 eV = 1.6 × 10^–19 J. The power output of the reactor is close to

125 MW

60 MW

54 MW

35 MW

JEE Main 2020 (Online) 8th January Evening Slot

MCQ (Single Correct Answer)

-1

An electron (mass m) with initial velocity $$\overrightarrow v = {v_0}\widehat i + {v_0}\widehat j$$ is in an electric field $$\overrightarrow E = - {E_0}\widehat k$$. If $$\lambda _0$$ is initial de-Broglie wavelength of electron, its de-Broglie wave length at time t is given by :

$${{{\lambda _0} } \over {\sqrt {1 + {{{e^2}{E^2}{t^2}} \over {{m^2}v_0^2}}} }}$$

$${{{\lambda _0}\sqrt 2 } \over {\sqrt {1 + {{{e^2}{E^2}{t^2}} \over {{m^2}v_0^2}}} }}$$

$${{{\lambda _0} } \over {\sqrt {1 + {{{e^2}{E^2}{t^2}} \over {2{m^2}v_0^2}}} }}$$

$${{{\lambda _0}} \over {\sqrt {2 + {{{e^2}{E^2}{t^2}} \over {{m^2}v_0^2}}} }}$$

PREVIOUS NEXT