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NEETPhysicsDual Nature of Matter

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): An LED fabricated from a semiconductor with a bandgap of 1.0 eV cannot emit light in the visible region. Reason (R): The wavelength of light emitted by a semiconductor with a 1.0 eV bandgap is approximately 1240 nm , which lies in the infrared region of the electromagnetic spectrum. In the light of

Options

  1. ABoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
  2. BBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
  3. CAssertion (A) is true but Reason (R) is false.
  4. DAssertion (A) is false but Reason (R) is true.

Correct answer

A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Step-by-step solution

The wavelength of the photon emitted by an LED is related to its bandgap energy by the equation = hc E_g . Using the standard approximation hc 1240 eV nm , for a semiconductor with a bandgap E_g = 1.0 eV : = 1240 eV nm 1.0 eV = 1240 nm . The visible spectrum ranges approximately from 400 nm to 700 nm . A wavelength of 1240 nm is significantly greater than 700 nm and falls in the infrared region. Therefore, the LED will emit infrared radiation and cannot emit visible light. Thus, both Assertion (A) and Reason (R) ar

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