In a hydrogen atom, the electron revolving in the fourth orbit, has angular momentum equal to _____.

(a)

h

(b)

\(\frac{h}{\pi}\)

(c)

\(\frac{4h}{\pi}\)

(d)

\(\frac{2h}{\pi}\)

The electric potential of an electron is given by \(V={ V }_{ 0 } \ In\left( \frac { r }{ { r }_{ 0 } } \right) \), where r₀ is a constant. If Bohr atom model is valid, then variation of radius of n^th orbit r_n with the principal quantum number n is _____.

(a)

\({ r }_{ n }∝ \frac { 1 }{ n } \)

(b)

\({ r }_{ n }∝ n\)

(c)

\({ r }_{ n }∝\frac { 1 }{ { n }^{ 2 } } \)

(d)

\({ r }_{ n }∝ { n }^{ 2 }\)

The nucleus is approximately spherical in shape. Then the surface area of nucleus having mass number A varies as _____.

(a)

A^2/3

(b)

A^4/3

(c)

A^1/3

(d)

A^5/3

The half-life period of a radioactive element A is same as the mean life time of another radioactive element B. Initially both have the same number of atoms. Then _____.

(a)

A and B have the same decay rate initially

(b)

A and B decay at the same rate always

(c)

B will decay at faster rate than A

(d)

A will decay at faster rate than B

The circumference of an electron's orbit of radius r must be an integral multiple of de Broglie wavelength that is ________________.

(a)

0.529 nl

(b)

\(\sqrt nλ\)

(c)

13.61

(d)

2ㅠr = nλ

In terms of Bohr radius a₀, the radius of the third Bohr orbit of a hydrogen atom is given by ______________.

(a)

8a_o

(b)

9a_o

(c)

6a_o

(d)

\(\sqrt 3\) a_o

The total energy of electrons in the ground state of a hydrogen atom is -13.6 eV. The k.E of an electron in the first excited state is ____________.

(a)

6.8 eV

(b)

13.6 eV

(c)

1.7 eV

(d)

3.4 eV

The minimum wavelength of the X-rays produced by electrons accelerated through a potential difference of V volts is directly proportional to _____________.

(a)

\(\frac { 1 }{ \sqrt { V } } \)

(b)

\(\frac { 1 }{ V } \)

(c)

\(\sqrt { V } \)

(d)

V²

J.J. Thomson's experiment demonstrated that ______________.

(a)

cathode rays are streams of negatively charged ions

(b)

all the mass of an atom is in the nucleus

(c)

specific charge of electrons is much greater than the protons.

(d)

e/m ratio changes when different gases is placed in the discharge tube

In a discharge tube, the source of positive rays is ________________.

(a)

cathode

(b)

anode

(c)

gas atoms present in the discharge tube

(d)

fluorescent screen

When an electric field is applied to an atom each of the spectral lines split into several lines. This effect is known as ________________.

(a)

Zeeman effect

(b)

Stark effect

(c)

Raman effect

(d)

Seebeck effect

In Millikan's experiment, the plates are kept at a distance of 16mm and are maintained at a potential difference of 10,000 V. The electric intensity is ______________.

(a)

62.5 V/m

(b)

6.25 x 10⁵ V/m

(c)

6.25 x 10³ V/m.

(d)

1.6 x 10⁵ Vim

The wave number of a spectral line of the hydrogen atom is equal to Rydberg's constant. The line is ______________.

(a)

first line of lyman series

(b)

series limit of lyman series

(c)

first line of pfund series

(d)

series limit of pfund sereis

Arrange the spectral lines H_α, H_β, H_γ, H_δ in the increasing order of their wavelength.

(a)

H_α, H_β, H_⋎, H_δ

(b)

H_δ, H_⋎, H_β, H_α

(c)

H_β, H_α H_δ, H_⋎

(d)

H_α, H_β, H_γ, H_δ

The direction of deflection shows that cathode rays are _________ in charge

(a)

negative

(b)

positive

(c)

neutral

(d)

oscillatory

In Millikan's experiment an oil drop of mass 4.9 x 10^-14 kg is balanced by applying potential difference of 2 kV between the two plates which are 2 mm apart. The charge of the drop is ________________

(a)

1.96 x 10^-18C

(b)

1.602 x 10^-19C

(c)

12 C

(d)

4.9 x 10^-19C

The orbits in which electrons supposed to be revolving according to Rutherford are ___________

(a)

square-shaped

(b)

circular

(c)

rectangular

(d)

linear

Bohr's radius gives the radius of the _________ orbit.

(a)

first

(b)

second

(c)

third

(d)

fourth

When the electron jumps from any of the outer orbits to the first orbit, spectral lines are emitted in the ________ region.

(a)

visible

(b)

IR

(c)

X-ray

(d)

UV

Paschen series of hydrogen atom comes under ___________ region.

(a)

IR

(b)

UV

(c)

X-ray

(d)

Gamma ray