Chapter 7: Q32P (page 386)

Verify Parseval’s theorem (12.24) for the special cases in Problems 31 to 33.
32. $f (x)$ and $g (α)$ as in problem 21.

Short Answer

Expert verified

$\int_{- \infty}^{\infty} {| g (α) |}^{2} d α = \frac{1}{2 π} \int_{- \infty}^{\infty} {| f (x) |}^{2} d x = \frac{σ}{2 \sqrt{π}}$ .Thus the Parseval theorem is confirmed.

Step by step solution

Given Information.

The given functions are $f (x) = e^{- \frac{x^{2}}{2 σ^{2}}}$ and $g (α) = \frac{σ}{\sqrt{2 π}} e^{- \frac{σ^{2} α^{2}}{2}}$ .Parseval theorem is to be verified for this special case.

Definition of Parseval’s theorem

Parseval’s theorem is a theorem stating that the energy of a signal can be expressed as its frequency components’ average energy.

Verify Parseval Theorem

It is known that Gaussian integral is $\int_{- \infty}^{\infty} e^{- x^{2}} d x = \sqrt{π}$

Use the Gaussian integral to verify Parseval theorem

$\begin{matrix} \frac{1}{2 π} \int_{- \infty}^{\infty} e^{\frac{- x^{2}}{σ^{2}}} d (x σ) σ = \frac{σ}{2 π} \sqrt{π} \\ = \frac{σ}{2 \sqrt{π}} \end{matrix}$

And

$\begin{matrix} \frac{σ^{2}}{2 π} \int_{- \infty}^{\infty} e^{- σ^{2} α^{2}} d (α σ) \frac{1}{σ} = \frac{σ}{2 π} \int_{- \infty}^{\infty} e^{- x^{2}} d x \\ = \frac{σ}{2 π} \sqrt{π} \\ = \frac{σ}{2 \sqrt{π}} \end{matrix}$

$\int_{- \infty}^{\infty} {| g (α) |}^{2} d α = \frac{1}{2 π} \int_{- \infty}^{\infty} {| f (x) |}^{2} d x = \frac{σ}{2 \sqrt{π}}$ .Thus the Parseval theorem is confirmed.

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Verify Parseval’s theorem (12.24) for the special cases in Problems 31 to 33.
32. $f (x)$ and $g (α)$ as in problem 21.

Short Answer

Step by step solution

Given Information.

Definition of Parseval’s theorem

Verify Parseval Theorem

One App. One Place for Learning.

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Verify Parseval’s theorem (12.24) for the special cases in Problems 31 to 33.32. f(x)and g(α)as in problem 21.

Short Answer

Step by step solution

Given Information.

Definition of Parseval’s theorem

Verify Parseval Theorem

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Physics Textbooks

Medical Physics

Dynamics

Turning Points in Physics

Electrostatics

Famous Physicists

Further Mechanics and Thermal Physics

Study anywhere. Anytime. Across all devices.

Verify Parseval’s theorem (12.24) for the special cases in Problems 31 to 33.
32. $f (x)$ and $g (α)$ as in problem 21.