Introduction

- In today’s article, we are going to study about ‘ Easiest explanation of
**Davisson and Germer experiment**class 12′ How beneficial it is and what is the Experimental setup of**Davisson and germer experiment**. We will also read about some more topics like explanation of**Davisson and Germer experiment**, conclusion of**Davisson and Germer experiment,**numerical based on**Davisson and Germer experiment**etc in Detail. So, take your notebooks in you hand and get ready to study physics in an easy and sorted way.

# Davisson and Germer experiment

Wave nature of particle was verified by davisson and germer experiment. The experimental figure is shown below. This experimental setup has three parts-

- Electron gun- It consist a tungsten filaments coated by barium oxide. The electron gun emits electron by giving power to the tungsten filament using law voltage power supply. A drift tube ‘A’ is used for focusing and accelerating electron beam. The energy of electron is controlled by high voltage power supply. This power supply apply a voltage difference between filament and tube A.
- Nickel Target- An nickel crystal is used as a target for electron beam.
- Movable collector- It is a hollow chamber filled CO2 or SO2 gas. This collector is connected to a galvanometer for measurement of current.

## Working of Davisson and Germer experiment

A electron beam is generated by a electron gun. The energy of electron beam is controlled by applying a fix voltage v. When this electron beam is diffracted by nickel crystal. Intensity of diffracting beam is measured by a movable collecter that is connected connected to a galvanometer. This experiment was repeated by varying potential value from 44v to 69v. And measure the intensity of beam at different angle.

If we plot a graph between direction of electron beam and potential v then we get at 54v. We get maximum pitch at 50° angle.

Then,

As we know from De-broglie principle,

λ= h/ √2mev

On putting the value of e,h,m and v then we get

λ= 12.27× 10^-10 / √v

λ= 12.27× 10^-10 m/ √54

And hence, λ= 1.65× 10^-10 m

λe = 1.65× 10^-10 × 10^9 nm

λe = 1.65× 10^-1

And λe = 0.165 nm

We know that for diffraction of wave-

nλ = d sinθ

If n= 1 and 2.15 A° because we takes known crystal (Nickel)

λ = d sinθ

λ = 2.15 × 10^-10 × sin 50°

And λ= 1.67× 10^-10 m

∴ sin θ= 0.766

λe = 1.67A°

λe = 0.167 nm

And, λe = 1.67× 10^-10 m

Above all these three values are Experimental value.

### Numerical based on Davisson and Germer experiment

Question 1 If intermolecular distance (d) is 4A° for a crystal if Maximum diffraction of beam is observed at 30° then find out its wavelength.

Solution- given that θ= 30° and d= 4A°

λ= ?

We know that,

λ = d sinθ

Hence on putting values we get,

λ = 4× 10^-10 × sin30°

λ = 4× 10^-10 × 1/2

And , λ = 2× 10^-10 m

Question 2- If intermolecular distance is 3A° for a crystal. A electron bean falling upon this crystal. Electron beam is given 1.5A° then find out interference angle.

Solution- Given that d= 3A °

λ = 1.5 A°

To find θ = ?

Hence, we know that

λ = d sinθ

Sin θ = λ/d

Sin θ = 1.5 A°/ 3A°

And, Sin θ = 15/30 = 1/2

Hence θ is 30°.