12th Class Physics MCQS
The first spectral lines were discovered in 1885, were
Paschen series
Pfund series
Bracket series
Balmer series
The radius of hydrogen atom is:
0.53A°
0.053A°
0.53 x 10-9
0.053 x10-9
Target material used in x-rays tube have following properties.
High atomic number and high melting pouint
Low atomic number and low melting pouint
High atomic number only
High atomic number and low melting pouint
An atom can reside in excited state for
More than one second
10-10 second
10-8 second
One second
The Balmer series is obtained when all the transition of electrons terminate on
2nd orbit
3rd orbit
1st orbit
4th orbit
X-rays were discovered by
None of these
Rontgen
Henry Becquerel
Curie
Frequency of x-rays depends upon.
Both B and C
Accelerating potencial
Nature of the target
Number of electrons striking target
For an atom of hydrogen atom the radius of the first orbit is given by:
me/4h2
h2 me2
h2/4
H/me2
Reflecting mirrors in laser is used to
For producing more energetic lasers
None of these
Further stimulation
Both (a) and (b)
The value of Rydberg constant is:
1.0749×107m-1
1.0974 x 10-7 m-1
1.0974 x 107 m-1
1.974 x106m-1
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