Question

For LED's to emit light in visible region of electromagnetic light, it should have energy band gap in the range of:

Options

• 0.9 eV to 1.6 eV

• 0.5 eV to 0.8 eV

• 0.1 eV to 0.4 eV

• 1.7 eV to 3.0 eV

Answer 1

1.7 eV to 3.0 eV

Explanation -

Visible light lies between 400 nm - 700 nm

Energy gap for 400 nm `"E"_("g"_1) = ("hc")/lambda = (1242  "in"  "eV")/(lambda   "in  nm")`

`"E"_("g"_1) = 1242/400 = 3.1  "eV"`

Energy gap for 700 nm `"E"_("g"_2) = 1242/700 "eV" = 1.77  "eV"`