Answer all the questions in the spaces provided. (a) The intensity of a progressive wave is defined as the average power transmitted through a surface per unit area. Show that the SI base units of intensity are $\text{kg s}^{-3}$. (i) The intensity $I$ of a sound wave is related to the amplitude $x_0$ of the wave by $$ I = K\rho cf^2x_0^2 $$ where $\rho$ is the density of the medium through which the sound is passing, $c$ is the speed of the sound wave, $f$ is the frequency…

Physics 9702/23 — October/November 2015

Cambridge AS Level · AS Level Structured Questions · worked solutions for every part, with the mark scheme

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Topics Dynamics · Work, Energy and Power · Waves · Superposition · Physical Quantities and Units · Kinematics · +5 more

Q1Physical Quantities and UnitsWavesFree sample

Answer all the questions in the spaces provided.

(a)

The intensity of a progressive wave is defined as the average power transmitted through a surface per unit area.

Show that the SI base units of intensity are $\text{kg s}^{-3}$ .

(b)

(i)

The intensity $I$ of a sound wave is related to the amplitude $x_0$ of the wave by

I = K\rho cf^2x_0^2

where $\rho$ is the density of the medium through which the sound is passing,
$c$ is the speed of the sound wave,
$f$ is the frequency of the sound wave
and $K$ is a constant.

Show that $K$ has no units.

(ii)

Calculate the intensity, in $\text{pW m}^{-2}$ , of a sound wave where

$K = 20$ ,
$\rho = 1.2$ in SI base units,
$c = 330$ in SI base units,
$f = 260$ in SI base units
and $x_0 = 0.24\ \text{nm}$ .

intensity = ______ $\text{pW m}^{-2}$

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