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Assertion: The semiconductor used for fa...

Assertion: The semiconductor used for fabrication of visible LEDs must at least have a band gap of 1.8 eV.
Reason: The spectral range of visible light is 0.4 eV to 1.8 eV

A

If both assertion and reason are true and reason is the correct explanation of assertion.

B

If both assertion and reason are true not but reason is not the correct explanation of assertion.

C

If assertion is true but reason is false

D

If both assertion and reason are false.

Text Solution

AI Generated Solution

The correct Answer is:
To solve the assertion and reason question regarding the band gap of semiconductors used for visible LEDs, we will analyze both the assertion and the reason step by step. ### Step 1: Understanding the Assertion The assertion states that "The semiconductor used for fabrication of visible LEDs must at least have a band gap of 1.8 eV." - **Explanation**: The band gap of a semiconductor is the energy difference between the valence band and the conduction band. For a semiconductor to emit visible light when electrons recombine with holes, the energy of the emitted photon must correspond to the energy of the band gap. ### Step 2: Understanding the Reason The reason states that "The spectral range of visible light is 0.4 eV to 1.8 eV." - **Explanation**: The visible spectrum of light ranges from approximately 400 nm (which corresponds to about 3.1 eV) to 700 nm (which corresponds to about 1.8 eV). This means that for a semiconductor to emit visible light, its band gap must be within this range. ### Step 3: Analyzing the Relationship Now, we need to analyze the relationship between the assertion and the reason. - The assertion claims that a band gap of at least 1.8 eV is necessary for visible LEDs. However, the reason indicates that the upper limit of the visible spectrum is 1.8 eV, which means that a band gap of exactly 1.8 eV would emit light at the edge of the visible spectrum. ### Step 4: Conclusion - The assertion is **partially correct** because while a band gap of 1.8 eV can produce light at the edge of the visible spectrum, it is not sufficient to cover the entire range of visible light. A band gap greater than 1.8 eV would not be suitable for visible LEDs as it would emit light outside the visible spectrum. - The reason is **correct** in stating the spectral range of visible light, but it does not fully support the assertion. ### Final Answer - The assertion is **incorrect** because a band gap of at least 1.8 eV is not necessary for all visible LEDs, while the reason is **correct** as it accurately describes the spectral range of visible light.
To solve the assertion and reason question regarding the band gap of semiconductors used for visible LEDs, we will analyze both the assertion and the reason step by step. ### Step 1: Understanding the Assertion The assertion states that "The semiconductor used for fabrication of visible LEDs must at least have a band gap of 1.8 eV." - **Explanation**: The band gap of a semiconductor is the energy difference between the valence band and the conduction band. For a semiconductor to emit visible light when electrons recombine with holes, the energy of the emitted photon must correspond to the energy of the band gap. ### Step 2: Understanding the Reason ...
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