2019-03-01_Physics_Times

The Hitomi satellite recently observed the Lyman

alpha emission line (n 2 to n 1 )of hydrogen-

like iron ion (atomic number of iron is 26) from the

perseus galaxy cluster. The wavelength of the line

is closest to

(a)2Å (b) 1 Å (c) 50 Å (d) 10 Å

A particle of mass m moves around the origin in a

potential 2 2

1

2

m r , where r is the distance from

the origin. Applying the Bohr model in this case,

the radius of particle in its nth orbit in terms of

a h/ (2 m )is

(a) a n (b) an (c) an^2 (d) an n

To calculate the size of a hydrogen anion using the

Bohr model, we assume that its two electrons move

in an orbit such that they are always on diametrically

opposite sides of the nucleus. With each electron

having the angular momentum h/ 2 , and

taking electron interaction into account the radius

of the orbit in terms of the

Bohr radius of hydrogen atom

2

0

2

4

B

h

a

me



 is

(a) aB (b)

4

3

aB (c)

2

3

aB (d)

3

2 B

a

An electron with kinetic energy E collides with a

hydrogen atom in the ground state. The collision

will be elastic

(a) For all values of E

(b) For E (^) 10.2eV
(c) For 10.2eV  E 13.6 eV only
(d) For 0E 3.4 eV only
The continuous part of X-ray spectrum is a result
of the
(a) photoelectric effect
(b) Raman effect
(c) Compton effect
(d) Inverse photoelectric effect
The wavelength of the first Balmer line caused by
a transition from the n 3 level to the n 2 level
in hydrogen is  1. The wavelength of the line
caused by an electronic transition from n 5 to
n 3 is
(a) 1
375
128
 (b) 1
125
64
 (c) 1
64
125
 (d)
Atomic Structure and X-rays

1. [2018]


2. 
   

   [2017]

   
   


3. 
   

   [2017]

   
   


4. 
   

   [2016]

   
   


5. 
   

   [2016]

   
   


6. 
   

   [2014]

   
   


7. 
   

   [2013]
   8
   [2012]
   1
   128
   375
   
   A singly ionized helium atom in an excited state
   ( 4)n emits a photon of energy 2.6 eV. Given that
   the ground state energy of hydrogen atom is 13.6
   eV, the energy ( )Et and quantum number (n) of the
   resulting state are respectively,
   (a) Et 13.6eV,,n 1
   (b)Et 6.0eV, n 3
   (c) Et 6.0eV, n 2
   (d) Et 13.6 eV, n 2

   
   

. In one model of the electron, the electron of mass
me is thought to be a uniformly charged shell of
radius R and total charge e, whose electrostatic
energy E is equivalent to its mass me via Einstein’ss

mass energy relation E m c e^2. In this model, R is

approximately (me 9.1 10^31 kg,c 3 10^8 ms^1 ,

9

1/ 4   0 9 10Farad

m^1 , magnitude of the

electron charge  1.6 10^19 C)