1
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
Both the nucleus and the atom of some element arein their respective first excited states. They get de-excted by emitting photons of wavelengths $$\lambda$$N, $$\lambda$$A respectively. The ratio $${{{}^\lambda N} \over {{}^\lambda A}}$$is closest to :
A
10$$-$$6
B
10
C
10$$-$$10
D
10$$-$$1
2
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
At some instant, a radioactive sample S1 having an activity 5 $$\mu$$Ci has twice the number of nuclei as another sample S2 which has an activity of 10 $$\mu$$Ci. The half lives of S1 and S2 are :
A
20 years and 5 years, respectively
B
20 years and 10years, respectively
C
5 years and 20 years, respectively
D
10 years and 20 years, respectively
3
JEE Main 2018 (Offline)
+4
-1
An electron from various excited states of hydrogen atom emit radiation to come to the ground state. Let $${\lambda _n}$$, $${\lambda _g}$$ be the de Broglie wavelength of the electron in the nth state and the ground state respectively. Let $${\Lambda _n}$$ be the wavelength of the emitted photon in the transition from the nth state to the ground state. For large n, (A, B are constants)
A
$${\Lambda _n} \approx A + {B \over {\lambda _n^2}}$$
B
$${\Lambda _n} \approx A + B{\lambda _n}$$
C
$$\Lambda _n^2 \approx A + B\lambda _n^2$$
D
$$\Lambda _n^2 \approx \lambda$$
4
JEE Main 2018 (Offline)
+4
-1
If the series limit frequency of the Lyman series is $${\nu _L}$$, then the series limit frequency of the Pfund series is:
A
$${\nu _L}/25$$
B
$$25{\nu _L}$$
C
$$16{\nu _L}$$
D
$${\nu _L}/16$$
JEE Main Subjects
Physics
Mechanics
Electricity
Optics
Modern Physics
Chemistry
Physical Chemistry
Inorganic Chemistry
Organic Chemistry
Mathematics
Algebra
Trigonometry
Coordinate Geometry
Calculus
EXAM MAP
Joint Entrance Examination