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UV light of the wavelength 800 A and 700 A falls on the hydrogen atoms in their ground state and liberates electrons with KE 1.8 eV and 4 eV respectively. Calculate Planck's constant.

UV light of the wavelength 800 A and 700 A falls on the hydrogen atoms in their ground state and liberates electrons with KE 1.8 eV and 4 eV respectively. Calculate Planck's constant.

Grade:11

1 Answers

Ramesh V
70 Points
13 years ago

KE = hc/λ - Wf       where  Wf is work function

1.8 = hc / 8*10-8  - Wf       .       ... (1)

4 = hc / 7*10-8  - Wf                  ....(2)

2.2 = hc*108 [1/7 - 1/8]

Plancks constat : h = 4.106 x 10-15 eV-sec  or  6.578 x 10-34 J-sec

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