The intensity at a point at a distance r from a source which produces cylindrical wavefronts varies as

Question

The intensity at a point at a distance r from a source which produces cylindrical wavefronts varies as (A) I propto (1/r2) (B) I propto (1/r) (C) I propto r0 (D) I propto (1/r3)

Tardigrade Admin · Accepted Answer

The intensity at a point at a distance r from a source varies as I propto (1/r) <img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/physics/f032433007797765589124865c2703cb-.png" /> This is because intensity is ( text Power / text Area ) and the surface area of wavefronts changes by 2 π r l.

Q. The intensity at a point at a distance $r$ from a source which produces cylindrical wavefronts varies as

$I \propto \frac{1}{r ^{2}}$

$I \propto \frac{1}{r}$

$I \propto r^{0}$

$I \propto \frac{1}{r ^{3}}$

The intensity at a point at a distance $r$ from a source varies as $I \propto \frac{1}{r}$

This is because intensity is $\frac{Power}{Area}$ and the surface area of wavefronts changes by $2 π r l$ .

Q. The intensity at a point at a distance r from a source which produces cylindrical wavefronts varies as

I∝r21​

I∝r1​

I∝r0

I∝r31​