<p>In the following questions, assume that light bulbs radiate uniformly in all

Question

<p>In the following questions, assume that light bulbs radiate uniformly in all directions and that <span>2.9</span><span>%</span> of their power is converted to light.</p>
<div class="indent">(a) Find the average intensity of light at a point <span>2.4</span> m from a 120-W red light bulb (<span><em>&#955;</em></span> = 710 nm).<br /><span class="qTextField"><input id="RN_1130874_0_0_1140323" dir="ltr" name="RN_1130874_0_0_1140323" size="10" type="text" /></span><img id="mark_RN_1130874_0_0_1140323" title="Your answer was incorrect, but has changed from what was graded." src="http://www.webassign.net/wastatic/wacache3416a75f4cea9109507cacd8e2f2aefc/common/img/cross_grey3.png" alt="Your answer was incorrect, but has changed from what was graded." /><br /><span>Did you accidentally divide or take the inverse in your calculation?</span> W/m² <br /><br />(b) Is the average intensity <span>2.4</span> m from a 120-W blue light bulb (<span><em>&#955;</em></span> = 480 nm) greater than, less than, or the same as the intensity found in part (a)?<br /><input id="RC_1130874_0_1_1140323" name="RC_1130874_0_1_1140323" type="hidden" value="mc" />
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<div class="markWrap container"><span class="correctBord"><span class="ms"><input id="RC_1130874_0_1_1140323_0" name="RC_1130874_0_1_1140323" type="radio" value="0" /><label for="RC_1130874_0_1_1140323_0">greater</label> </span><span class="ms"><input id="RC_1130874_0_1_1140323_1" name="RC_1130874_0_1_1140323" type="radio" value="1" /><label for="RC_1130874_0_1_1140323_1">lesser</label>&#160;&#160;&#160;&#160; </span><span class="ms"><input id="RC_1130874_0_1_1140323_2" checked="checked" name="RC_1130874_0_1_1140323" type="radio" value="2" /><label for="RC_1130874_0_1_1140323_2">the same</label> </span><span class="mark"><img id="mark_RC_1130874_0_1_1140323" title="Your answer is correct." src="http://www.webassign.net/wastatic/wacache3416a75f4cea9109507cacd8e2f2aefc/common/img/tick.png" alt="Your answer is correct." /></span></span></div>
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<br />&#160;<br /><br /><br />(c) Calculate the average intensity for part (b).<br /><span class="qTextField"><input id="RN_1130874_0_3_1140323" dir="ltr" name="RN_1130874_0_3_1140323" size="10" type="text" /></span> W/m²</div>

Explanation / Answer

The power of the bulb P = 120 W The distance from the source r = 2.3 m (a) The average intensity                  I = P/A = 2.9% (120 W) / 4(2.3)^2                     = 0.052 W/m^2 Since the intensity of the bulb is not depends upon the wavelength of the light so the bulb B also have same intensity 0.052 W/m^2        

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