Conductivity of a photodiode starts changing only if the wavelength of incident light is less than 660 nm. The band gap of photodiode is found to be (X/8) eV. The value of X is: (Given, h = 6.6 × 10⁻³⁴ J s, e = 1.6 × 10⁻¹⁹ C)
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Question

Conductivity of a photodiode starts changing only if the wavelength of incident light is less than 660 nm. The band gap of photodiode is found to be (X/8) eV. The value of X is: (Given, h = 6.6 × 10⁻³⁴ J s, e = 1.6 × 10⁻¹⁹ C)

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G1 Physics · Accepted Answer

Band-gap energy: E(g) = hc/λ = [6.6 × 10⁻³⁴ × 3 × 10⁸]/[660 × 10⁻⁹] = 3 × 10⁻¹⁹ J Converting into eV: E(g) = (3 × 10⁻¹⁹)/(1.6 × 10⁻¹⁹) = 15/8 eV Given: E(g) = X/8 eV Therefore, X = 15