Following results are observed when sodium metal is irradiated with different wavelengths. Calculate (a) Threshold wavelength and, (b) Planck's constant.

λ (nm)

500

450

400

**v * 10^–5 (cm s^–1)

2.55

4.35

5.35**

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Alok Kumar Singh | Contributor-Level 10

9 months ago

Let the threshold wavelength be λ₀ nm or λ₀ * 10⁻⁹ m.

h (ν−ν₀) = ½ mv²

hc (1/λ−1/λ₀)= ½ mv²

hc [ (1/500*10⁻⁹) – (1/ λ₀*10⁻⁹)] = ½ m (2.55*10⁶)² . (1)

Similarly,

hc [ (1/450*10⁻⁹) – (1/λ₀? *10⁻⁹? )] = ½? m (4.35*10⁶)² . (2)

Similarly,

hc [ (1/400*10⁻⁹) – (1/λ₀? * 10⁻⁹? )] = ½? m (5.2 * 10⁶)² . (3)

Divide

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λ (nm)	500	450	400
*v 10^–5 (cm s^–1)**	2.55	4.35	5.35

Following results are observed when sodium metal is irradiated with different wavelengths. Calculate (a) Threshold wavelength and, (b) Planck's constant. λ (nm) 500 450 400 v * 10–5 (cm s–1) 2.55 4.35 5.35