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Q71CE

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Modern Physics
Found in: Page 1
Modern Physics

Modern Physics

Book edition 2nd Edition
Author(s) Randy Harris
Pages 633 pages
ISBN 9780805303087

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Short Answer

(a) Find the wavelength of a proton whose kinetic energy is equal 10 its integral energy.

(b) ' The proton is usually regarded as being roughly of radius 10-15m. Would this proton behave as a wave or as a particle?

(a) The wavelength of a proton that has kinetic energy equal to its internal energy is 7.63×10-16m

(b) The moving proton would behave like as a particle in nature.

See the step by step solution

Step by Step Solution

Step 1: Given data

Mass of proton, m=1.67×10-27kg Speed of light, c=3.0×108m/s Plank's constant, h=6.63×10-34J.s

Step 2: Relativistic effect in de Broglie's equation

The internal energy E of an object is

E=mc2

The equation for the kinetic energy ( KE) of an object traveling at relativistic velocities is

KE=(γu-1)mc2

Where, m is rest mass, and c is the speed of light.

De Broglie's wavelength

λ=hp

Where, p is the momentum.

Relativistic effect in de Broglie's equation

λ=hγumv

Where, is the velocity at which the protons kinetic energy equals its internal energy, and γ is Lorentz factor.

Speed at which the internal energy become equal to the kinetic energy

mc2=(γu-1)1=γu-12=γu

Lorentz factor is given by a relation,

γu=11-v2c2 2=11-v2c21-v2c2=12 1-v2c2=14 v2c2=34 v=32c

Step 3: Substitute the value of velocity in wavelength, 

(a)

Substitute the value of velocity in wavelength λ,

The wavelength of a proton that has kinetic energy equal to its internal energy is given by,

λ=hγm3c2

Substitute 6.63×10-34J.s for h, 1.67×10-27 kg for m and 3.0 ×108m/s for c in the above equation to solve for λ

λ=6.63×10-34J.s(2)(1.67×10-27kg)(3×3.0×108m/s2 =7.63×10-16m

Hence, the wavelength of a proton that has kinetic energy equal to its internal energy is λ=7.63×10-16m

Step 4: Explain proton behavior

(b)

The wavelength of a proton that has kinetic energy equal to its internal energy is λ=7.63×10-16m

As the wavelength of the proton is smaller than the roughly size of the proton .

(10-15m)So, the moving proton would behave like as a particle in nature.

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