JEE MAIN - Physics (2021 - 26th February Morning Shift - No. 5)
LED is constructed from Ga-As-P semiconducting material. The energy gap of this LED is 1.9 eV. Calculate the wavelength of light emitted and its colour.
[h = 6.63 $$\times$$ 10$$-$$34 Js and c = 3 $$\times$$ 108 ms$$-$$1]
[h = 6.63 $$\times$$ 10$$-$$34 Js and c = 3 $$\times$$ 108 ms$$-$$1]
654 nm and orange colour
654 nm and red colour
1046 nm and red colour
1046 nm and blue colour
Explanation
We know that $$E = {{hc} \over \lambda }$$
$$\lambda = {{hc} \over E} \Rightarrow {{1240(in\,eV)} \over {E(in\,eV)}}$$
$$\lambda = {{1240} \over {1.9}}$$
= 652.63 nm $$ \approx $$ 654 nm
Wavelength of red light is 620 nm to 750 nm
$$\lambda = {{hc} \over E} \Rightarrow {{1240(in\,eV)} \over {E(in\,eV)}}$$
$$\lambda = {{1240} \over {1.9}}$$
= 652.63 nm $$ \approx $$ 654 nm
Wavelength of red light is 620 nm to 750 nm
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