KVPY Government Jobs Exams

Due to transitions among its first three energy levels, hydrogenic atom emits radiation at three discrete
wavelengths λ1, λ2, and λ3 (λ1 < λ2 < λ3). Then -
(A) λ1 = λ2 + λ3 (B) λ1 + λ2 = λ3 (C) 1/λ1 + 1/λ2 = 1/λ3 (D) 1/λ1 = 1/λ2 + 1/λ3

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KVPY Other Question

An electron collides with a free molecules initially in its ground state. The collision leaves the molecules in
an excited state that is metastable and does not decay to the ground state by radiation. Let K be the sum of
the initial kinetic energies of the electron and the molecule, and P
r
the sum of their initial momenta. Let K'
and P' represent the same physical quantities after the collision. Then -
(A) K = K', P = P' (B) K' < K, P = P' (C) K = K', P ≠ P' (D) K' < K, P ≠ P' The total radiative power emitted by spherical blackbody with radius R and temperature T is P. If the radius
if doubled and the temperature is halved then the radiative power will be -
(A) P/4 (B) P/2 (C) 2P (D) 4P