KCET2015PhysicsWave Optics
An LED is constructed from a pn junction based on a certain semi-conducting material whose energy gap is ( 1.9 eV ). Then the wavelength of the emitted light is
Options
- A( 2.9 10⁻⁹ m )
- B( 1.6 10⁻⁸ ~m )
- C( 6.5 10⁻⁷ ~m )
- D( 9.1 10⁻⁵ ~m )
Correct answer
C. ( 6.5 10⁻⁷ ~m )
Step-by-step solution
Energy gap, ( E_ g = h c ) Given ( E_ g =1.9 eV =1.9 1.6 10⁻¹⁹ ) Therefore, ( = h c E_ g = 6.6 10⁻³⁴ 3 10⁸ 1.9 1.6 10⁻¹⁹ =6.513 10⁻⁷ ~m 6.5 10⁻⁷ ~m ) Thus, wave length of emitted light is ( 6.5 10⁻⁷ ~m )