Directions : In the following questions, A statement of Assertion (A)...
So, vRMS ∝ √T Again de-Broglie wavelength, λ = h/mv
So, λ ∝ 1/√T
Hence, assertion and reason both are true and reason explains the assertion.
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Directions : In the following questions, A statement of Assertion (A)...
**Assertion (A):** The de-Broglie wavelength of a gas molecule is inversely proportional to the square root of temperature.
**Reason (R):** The root mean square velocity of gas molecules depends on temperature.
The correct answer is option 'A'. Let's understand why.
**Explanation:**
**De-Broglie Wavelength (λ):**
- According to de-Broglie's hypothesis, every particle with momentum exhibits wave-like properties.
- The de-Broglie wavelength (λ) is the wavelength associated with a moving particle and is given by the equation λ = h/p, where h is Planck's constant and p is the momentum of the particle.
**Root Mean Square Velocity (v_rms):**
- The root mean square velocity of gas molecules is a measure of the average velocity of the gas particles.
- It is given by the equation v_rms = √(3RT/M), where R is the gas constant, T is the temperature, and M is the molar mass of the gas.
**Inversely Proportional Relationship:**
- The de-Broglie wavelength (λ) and the root mean square velocity (v_rms) are related to each other.
- According to the kinetic theory of gases, the average kinetic energy of gas molecules is directly proportional to the temperature.
- The kinetic energy of a gas molecule is given by the equation KE = (1/2)mv^2, where m is the mass of the gas molecule and v is its velocity.
- As the temperature increases, the average kinetic energy of the gas molecules increases, resulting in an increase in their velocity.
- Since the de-Broglie wavelength is inversely proportional to the momentum (λ = h/p), an increase in velocity leads to a decrease in the de-Broglie wavelength.
- Therefore, the de-Broglie wavelength of a gas molecule is inversely proportional to the square root of the temperature.
**Conclusion:**
- The root mean square velocity of gas molecules depends on the temperature, as stated in Reason (R).
- The de-Broglie wavelength of a gas molecule is inversely proportional to the square root of temperature, as stated in Assertion (A).
- Reason (R) provides the correct explanation for Assertion (A), as the increase in temperature leads to an increase in the velocity of gas molecules, resulting in a decrease in their de-Broglie wavelength.