Question

A metal with work 2.21 ev is irradiated with a radiation of wavelenght 200 nm. what is the speed of fastest photo-electron emitted?​

Answer 1

Answer:

Speed of fastest electron = 1.186×10^6 m/s

Explanation:

Work function of metal,Wo = 2.21 eV

Energy associated with wavelength 200 nm, E= hc/λ

E= (6.626 × 10^-34 J-s)×(3×10^8)/ (200 ×10^-9)

E=9.939×10^-19 J

E=9.939×10^-19×0.6242×10^19=6.2 eV

Kinetic energy= E-Wo

⇒K.E = 6.2eV-2.21eV = 3.99eV ≈ 4 eV

K.E = $\frac{1}{2} mv^{2}$

⇒4×1.602×10^-19J = 1/2 × 9.1 × 10^-31 × v^2

⇒1.186×10^6 m/s=v

Speed of fastest electron = 1.186×10^6 m/s

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