AIIMS 2005 Physics Diode Lasers Assertion Reason Question

To analyze the given question regarding diode lasers in optical communication, let’s break down the assertion and reason, and then determine the correct answer.

Assertion:

Diode lasers are used as optical sources in optical communication.

This statement is true. Diode lasers are indeed commonly used in optical communication systems. They serve as efficient light sources for transmitting information over optical fibers. The advantages of diode lasers include their ability to produce coherent light, which is essential for long-distance communication, and their compact size, making them suitable for integration into various devices.

Reason:

Diode lasers consume less energy.

This statement is also true. Diode lasers are known for their energy efficiency compared to other light sources, such as incandescent or gas lasers. They operate at lower power levels while providing sufficient output for data transmission.

Conclusion on the Correct Answer:

Now, the key aspect we need to evaluate is whether the reason given directly explains the assertion. Although both statements are true, the reason does not specifically explain why diode lasers are used in optical communication. The assertion is primarily based on the performance characteristics of diode lasers, such as their efficiency, compactness, and ability to modulate quickly, rather than solely on their lower energy consumption.

Thus, the correct answer is: B) Both assertion and reason are true but reason is not the correct explanation of assertion.

Clarification of Other Options:

• Option A: Both assertion and reason are true, and reason is the correct explanation of assertion. This is incorrect because, while both statements are true, the reason does not satisfactorily explain the assertion.

• Option C: Assertion is true but reason is false. This is incorrect because both the assertion and the reason are true.

• Option D: Both assertion and reason are false. This is incorrect as both statements are actually true.

Key Concepts:

1. Diode Laser Functionality: A diode laser operates based on the principle of stimulated emission of radiation, allowing it to emit coherent light. The basic equation governing the relationship between the energy of the emitted photons and the wavelength of the light in a laser is given by:

   $E = \frac{hc}{\lambda}$

   where:

   • $E$ is the energy of the photon,
   • $h$ is Planck's constant ($6.626 \times 10^{-34} \, \text{Js}$),
   • $c$ is the speed of light in vacuum ($3 \times 10^8 \, \text{m/s}$),
   • $\lambda$ is the wavelength of the emitted light.

2. Energy Efficiency: Diode lasers are more energy-efficient than traditional lasers. Their operation typically involves a lower threshold current and higher optical output, which contributes to their lower energy consumption.

In summary, the assertion correctly identifies the role of diode lasers in optical communication, while the reason highlights an important characteristic of diode lasers, but it does not directly explain their use in that context.