# Chemistry Class 11 NCERT Solutions: Chapter 2 Structure of Atom Part 18

Q: 56 Calculate the wavelength for the emission transition if it starts from the orbit having radius nm and ends at pm. Name the series to which this transition belongs and the region of the spectrum.

Answer:

The radius of the orbit of hydrogen-like particles is given by,

For radius

Similarly,

Thus, the transition is from the orbit to the orbit. It belongs to the Balmer series.

Wave number for the transition is given by,

Wavelength associated with the emission transition is given by,

Q: 57 Dual behaviour of matter proposed by de Broglie led to the discovery of electron microscope often used for the highly magnified images of biological molecules and other type of material. If the velocity of the electron in this microscope is calculate de Broglie wavelength associated with this electron.

Answer:

From de Broglie’s equation,

Q: 58. Similar to electron diffraction, neutron diffraction microscope is also used for the determination of the structure of molecules. If the wavelength used hare is 800 pm, calculate the characteristic velocity associated with the neutron.

Answer:

From de Broglie’s equation,

Where,

V= velocity of particle (neutron)

h =Planck’s constant

m = Mass of particle (neutron)

Substituting the values in the expression of velocity (v),