Line Spectra

Q.

If the momentum of an electron is changed by P, then the de-Broglie wavelength associated with it changes by 0.5%. The initial momentum of electron will be:

1. 100P

2. 200P

3. 400P

4. $\frac{P}{200}$

Q. The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is

1. $2:1$
2. $4:1$
3. $2:6$
4. $1:2$

Q.

The work function of caesium metal is 2.14 eV. When light of frequency 6 ×10¹⁴ Hz is incident on the metal surface, photoemission of electrons occurs. What is the

(a) maximum kinetic energy of the emitted electrons,

(b) Stopping potential, and

(c) maximum speed of the emitted photoelectrons?

Q. The wavelength of the first spectral line in the Balmer series of hydrogen atom is $6561\stackrel{\circ }{A}$. The wavelength of the second spectral line in the Balmer series of singly-ionized helium atom is

1. $1215\stackrel{\circ }{A}$
2. $1640\stackrel{\circ }{A}$
3. $2430\stackrel{\circ }{A}$
4. $4687\stackrel{\circ }{A}$

Q.

Which of the following series in the spectrum of hydrogen atom lies in the visible region of the electromagnetic spectrum?

1. Paschen series

2. Balmer series

3. Lyman series

4. Brackett series

Q. The short wavelength limit for the Lyman series of the hydrogen spectrum is $913.4A^{\circ }$. Calculate the short wavelength limit for Balmer series of the hydrogen spectrum.

Q. Hydrogen atom emits blue light when it changes from n = 4 energy level to n = 2 level. Which colour of light would the atom emit when it changes from n = 5 level to n = 2 level

1. Red
2. Yellow
3. Green
4. Violet

Q.

Explain what is the hydrogen emission spectrum in detail?

Q. The Lyman series of hydrogen spectrum lies in

1. infrared region
2. visible region
3. ultraviolet region
4. region of X-ray

Q. electron has energy of 100eV what will be its wavelengt

Q.

The wavelength of the first line of lyman series for hydrogen atom is equal to that of the second line of Balmer series for a hydrogen like ion. The atomic number Z of hydrogen like ion is:

1. 4

2. 1

3. 2

4. 3

Q. Which of the following wavelength will be absent from the X-ray spectrum if the X-ray tube is operated at 40, 000 V?

1. $0.2A^{\circ }$
2. $0.5A^{\circ }$
3. $1.0A^{\circ }$
4. $2.0A^{\circ }$

Q. Electrons in hydrogen-like atoms $(Z=3)$ make transitions from the fifth to the fourth orbit and from the fourth to the third orbit. The resulting radiations are incident normally on a metal plate and eject photoelectrons. The stopping potential for the photoelectrons ejected by the shorter wavelength is 3.95 volts. Calculate the work function of the metal, and the stopping potential(in V) for the photoelectrons ejected by the longer wavelength.
$(\text{Rydberg constant}=1.094\times {10}^7{m}^{-1})$

Q.

Name spectral series of hydrogen which lies in the ultraviolet

Q. In a hydrogen like atom, an electron is orbiting in an orbit having quantum number $n$. Its frequency of revolution is found to be $13.2\times {10}^{15}Hz$. Energy required to remove this electron from the orbit is $54.4eV$. In the time of 7 nanosecond the electron jumps from$nth$ orbit to the orbit having quantum number $\frac{n}{2}$. If $\tau$ be the average torque acted on the electron during the above process, then find $\frac{T\times {10}^{27}}{3}$ (in $Nm$). (Given:$\frac{h}{\pi }=2.1\times {10}^{-34}Js,$ frequency of revolution of electron in the ground state of H atom is ${\nu }_0=6.6\times {10}^{15}Hz$ and ionization energy of H atom is $E_0=13.6eV$

1. 5
2. 4
3. 3
4. 2

Q. Two photons of energy 2.5 eV each is incident on a metal surface at the same time, if its work function is 4.5 eV, the metal surface 1. emits single electron 2. emits two electrons 3. emits more than two electrons 4. emits no electron

Q.

Fraunhofer lines are obtained in:

1. Solar spectrum

2. The spectrum obtained from the neon lamp

3. Spectrum from a discharge tube

4. None of the above

Q. The longest wavelength emitted in hydrogen atom belonging to Balmer series is ($R$ is Rydberg constant)

1. $\frac{36}{7R}$
2. $\frac{16}{3R}$
3. $\frac{36}{5R}$
4. $\frac{16}{7R}$

Q.

What is Raman spectroscopy? Is a type of line or continuous spectrum?

Q. Balmer series was observed and analysed for hydrogen before other series. A possible reason for this is

1. because it was relatively difficult to observe balmer series
2. because balmer series emissions were slowest & can be trapped for analysis
3. because balmer were of ultraviolet region
4. because balmer emissions of hydrogen were in visible range

Q.

Is the sun red shifted or blue shifted?

Q. A photon of $1.7\times {10}^{-13}$ Joules is absorbed by a material under special circumstances. The correct statement is

1. Electrons of the atom of absorbed material will go the higher energy states
2. Electron and positron pair will be created
3. Only positron will be produced
4. Photoelectric effect will occur and electron will be produced

Q. An electron in the hydrogen atom jumps from excited state n to the ground state.The wavelength so emitted illuminates a photosensitive material having work function 2.75 EV.If the stopping potential of photoelectron is 10 V, then the value of n is?

Q. If a photon and an electron have got same de broglie wavelength , then why total energy of electron is more than that of photon?

Q. The ratio of minimum wavelength of Lyman and Balmer series will be:

1. 1.25
2. 0.25
3. 5
4. 10

Q. The Lyman series of hydrogen spectrum lies in

1. infrared region
2. visible region
3. ultraviolet region
4. region of X-ray

Q. If $f_1$ is the frequency of the series limit of Lyman series, $f_2$ is the frequency of first line of Lyman series and $f_3$ is the frequency of the series limit of the Balmer series then:

1. $f_1-f_2=f_3$
   
2. $f_1=f_2-f_3$
   
   
3. $\frac{1}{f_2}=\frac{1}{f_1}+\frac{1}{f_3}$
4. $\frac{1}{f_1}=\frac{1}{f_2}+\frac{1}{f_3}$

Q. There are only three hydrogen atoms in a discharge tube. The analysis of spectrum shows that in all the hydrogen atoms, electrons are de-exciting from the fourth orbit. What should be the maximum number of spectral lines?

1. $6$
2. $1$
3. $4$
4. $5$

Q.

The _______ consists of well-defined lines of definite frequencies.

Q. Calculate the shortest and longest wavelengths of Balmer series of hydrogen atom. Given $R=1.097\times {10}^7{m}^{-1}$.