Download App

Atoms — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsAtoms2 Marks
Question
Electrons are emitted from an electron gun at almost zero velocity and are accelerated by an electric field E through a distance of 1.0m. The electrons are now scattered by an atomic hydrogen sample in ground state. What should be the minimum value of E so that red light of wavelength 656.3nm may be emitted by the hydrogen?
✓

Answer

The given wavelength in Balmer series.
The first line, which requires minimum energy is from $n_1=3$ to $n_2=2$
$\therefore$ The energy should be equal to the energy required for transition from ground state to n = 3
i.e., $\text{E}=13.6\Big[1-\Big(\frac{1}{9}\Big)\Big]=12.09\text{eV}$
$\therefore$ Minimum value of electric field = 12.09v/m = 12.1v/m

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "2 Marks Questions" from Atoms→Atoms — all question types→Physics STD 12 Science question papers→Gujarat Board STD 12 Science question papers→Gujarat Board question paper generator→

Similar questions

A ray PQ incident normally on the refracting face BA is refracting in the prism BAC made of material of refractive index1.5. Complete the path of ray through the prism. From which face will the ray emerge? Justify your answer.
→
A farsighted person cannot see objects placed closer to 50cm. Find the power of the lens needed to see the objects at 20cm.
→
A convex lens (n = 1.5) of focal length fa is immersed.
  1. In water n = 1.33 and.
  2. In carbon disulphide n = 1.6, how does the lens behave in the two cases?
→
Light from Balmer series of hydrogen is able to eject photoelectrons from a metal. What can be the maximum work function of the metal?
→
If an electric dipole is placed at an angle of $30^{\circ}$ to an electric field of intensity $2 \times 10^5 N / C$, a torque of 4 Nm is applied on it. If the length of the dipole is 2 cm , then what will be charge?
→
Explain J J. Thomson's plum pudding model of atom.
→
A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian has its north tip down at 60° with the horizontal. The horizontal component of the earth's magnetic field at the place is known to be 0.4 G. Determine the magnitude of the earth's magnetic field at the place.
→
The charge on a proton is $+1.6 \times 10^{-19} \mathrm{C}$ and that on an electron is $-1.6 \times 10^{-19} \mathrm{C}$. Does it mean that the electron has a charge 3.2 $\times 10^{-19} \mathrm{C}$ less than the charge of a proton?
→
Two identical circular loops, P and Q. each of radius r and carrying currents are kept in the parallel planes having a common axis passing through O. The direction of current in P is clockwise and in Q is anti-clockwise as seen from O which is equidistant from the loops P and Q. Find the magnitude of the net magnetic field at O.

Image
→
Explain the structure of Polaroid.
→