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Chapter 3: Q25E (page 93)

You are an early 20th-century experimental physicist and do not know the value of Planck's constant. By a suitable plot of the following data, and using Einstein's explanation of the photoelectric effect (KE=W鈭�蠒. where his not known), determine Planck's constant.

Short Answer

Expert verified

Planck's constanth=6.665脳10鈭�34J鈰�s

Step by step solution

01

Concept  and  Formula  

Energy E=hf鈭�蠒

Here, E is the energy,f is the frequency and 蠒is the work function.

E=eV0. Here,E is the kinetic energy, is the electronic charge and is the stopping potential.

c=蹿位Here, cis the speed of light, fis the frequency and 位is the wavelength.

Electronic charge=1.602脳10鈭�19C

Speed of light =2.99脳108m鈰�s鈭�1 .

02

Evaluate energy

Energy is given as,

E=hf鈭�蠒E=eV0eV0=hf鈭�蠒V0=hfe鈭�蠒e

Substituting c=蹿位

V0=hc别位鈭�蠒eV0=hce脳1位鈭�蠒e

03

Plot the graph

Plotting a graph of1位 versus V0 using the given data,

04

Calculate Planck’s constant

From the graph, gradient =1244V鈰�nmand intercept =鈭�2.2017V

As gradient =hce

1244=hceh=1244脳er

Substitute values for e and c

h=1244V鈰�nm脳1.602脳10鈭�19C2.99脳108m鈰�s鈭�1h=1244脳10鈭�9V鈰�m脳1.602脳10鈭�19C2.99脳108m鈰�s鈭�1h=6.665脳10鈭�34J鈰�s

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