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Class 12
Physics
Dual Nature Of Radiation And Matter
a for what kinetic energy of a neutron will the...

Question:
(a) For what kinetic energy of a neutron will the associated de Broglie wavelength be 1.40 × 10 ⁻¹⁰ m?

(b) Also find the de Broglie wavelength of a neutron, in thermal equilibrium with matter, having an average kinetic energy of (3/2) kT at 300 K.

Answer:

(a) De Broglie wavelength of the neutron, λ = 1.40 × 10 ⁻¹⁰ m

Mass of a neutron, m _n = 1.66 × 10 ⁻²⁷ kg

Planck’s constant, h = 6.6 × 10 ⁻³⁴ Js

Kinetic energy (K) and velocity (v) are related as:

K = 1/2 m_nv² ... (1)

De Broglie wavelength (λ) and velocity (v) are related as:

λ = h/ m_nv ....(2)

Using equation (2) in equation (1), we get:

Hence, the kinetic energy of the neutron is 6.75 × 10 ⁻²¹ J or 4.219 × 10 ⁻² eV.

(b) Temperature of the neutron, T = 300 K

Boltzmann constant, k = 1.38 × 10 ⁻²³ kg m ² s ⁻² K ⁻¹

Average kinetic energy of the neutron:

K' = 3/2 kT

= 3/2 x 1.38 x 10^-23 x 300 = 6.21 x 10^-21 J

The relation for the de Broglie wavelength is given as:

Therefore, the de Broglie wavelength of the neutron is 0.146 nm.

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Question:
(a) For what kinetic energy of a neutron will the associated de Broglie wavelength be 1.40 × 10 ⁻¹⁰ m?

(b) Also find the de Broglie wavelength of a neutron, in thermal equilibrium with matter, having an average kinetic energy of (3/2) kT at 300 K.

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Question: (a) For what kinetic energy of a neutron will the associated de Broglie wavelength be 1.40 × 10 −10 m? (b) Also find the de Broglie wavelength of a neutron, in thermal equilibrium with matter, having an average kinetic energy of (3/2) kT at 300 K.

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Question:
(a) For what kinetic energy of a neutron will the associated de Broglie wavelength be 1.40 × 10 ⁻¹⁰ m?

(b) Also find the de Broglie wavelength of a neutron, in thermal equilibrium with matter, having an average kinetic energy of (3/2) kT at 300 K.