The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is
2
1
4
4
C.
4
For the last Balmer Series
A photo-cell employs photoelectric effect to convert
change in the frequency of light into a change in electric voltage
change in the intensity of illumination into a change in photoelectric current
change in the intensity of illumination into a change in the work function of the photocathode
change in the intensity of illumination into a change in the work function of the photocathode
B.
change in the intensity of illumination into a change in photoelectric current
In photoelectric effect when monochromatic radiations of suitable frequency fall on the photo-sensitive plate called cathode, the photoelectrons are emitted which get accelerated towards anode. These electrons flow in the outer circuit resulting in the photoelectric current.
Using the incident radiations of a fixed frequency, it is found that the photoelectric current increases linearly with the intensity of incident light as shown in figure. Hence, a photocell employs photoelectric effect to convert change in the intensity of illumination into a change in photoelectric current.
Ionization potential of hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. According to Bohr's theory, the spectral lines emitted by hydrogen will be
two
three
four
four
B.
three
Ionization energy corresponding to ionization potential = -13.6 eV.
Photon energy incident = 12.1 eV
So, the energy of electron in excited state
= -13.6 + 12.1 = -1.5 eV
i.e.,
i.e., energy of electron in excited state corresponds to third orbit.
The possible spectral lines are when electron jumps from orbit 3rd to 2nd; 3rd to 1st and 2nd to 1st. Thus, 3 spectral lines are emitted.
The total energy of an electron in the ground state of a hydrogen atom is -13.6 eV. The kinetic energy of an electron in the first excited state is:
3.4 eV
6.8 eV
13.6 eV
13.6 eV
A.
3.4 eV
The total energy of an electron in the orbit is equal to negative of its kinetic energy.
The energy of hydrogen atom when the electron revolves in nth orbit is
E = -13.6/n2 eV
In the ground state: n =1
E = - -13.6/12 = -13.6 eV
For n = 2, E = -13.6/22 = -3.4 eV
so, the kinetic energy of an electron in the first excited state (i,e, for n = 2 ) is
K = - E = - (-3.4) - 3.4 eV