Bài 30: Giải bài toán về hệ thấu kính
Hướng dẫn giải Bài 4 (Trang 195 SGK Vật lý 11)
<p>4. Một hệ thấu kính gồm hai thấu kính <span id="MathJax-Element-1-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math>"><span id="MJXc-Node-1" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-2" class="mjx-mrow"><span id="MJXc-Node-3" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-4" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> và <span id="MathJax-Element-2-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math>"><span id="MJXc-Node-6" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-7" class="mjx-mrow"><span id="MJXc-Node-8" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-9" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> đồng trục có tiêu điểm ảnh chính của <span id="MathJax-Element-3-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math>"><span id="MJXc-Node-11" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-12" class="mjx-mrow"><span id="MJXc-Node-13" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-14" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> trùng với tiêu điểm vật chính của <span id="MathJax-Element-4-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math>"><span id="MJXc-Node-16" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-17" class="mjx-mrow"><span id="MJXc-Node-18" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-19" class="mjx-mi"></span></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math>. Chiếu một chùm tia sáng song song với <span id="MathJax-Element-5-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math>"><span id="MJXc-Node-21" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-22" class="mjx-mrow"><span id="MJXc-Node-23" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-24" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> theo phương bất kì. </p>
<p>a) Chứng minh chùm tia ló ra khỏi <span id="MathJax-Element-6-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math>"><span id="MJXc-Node-26" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-27" class="mjx-mrow"><span id="MJXc-Node-28" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-29" class="mjx-mi"></span></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math> cũng là chùm tia song song.</p>
<p>b) Vẽ đường đi của chùm tia sáng ứng với các trường hợp:</p>
<p><span id="MathJax-Element-7-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math>"><span id="MJXc-Node-31" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-32" class="mjx-mrow"><span id="MJXc-Node-33" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-34" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> và <span id="MathJax-Element-8-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math>"><span id="MJXc-Node-36" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-37" class="mjx-mrow"><span id="MJXc-Node-38" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-39" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> đều là thấu kính hội tụ.</p>
<p><span id="MathJax-Element-9-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math>"><span id="MJXc-Node-41" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-42" class="mjx-mrow"><span id="MJXc-Node-43" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-44" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> là thấu kính hội tụ; <span id="MathJax-Element-10-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math>"><span id="MJXc-Node-46" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-47" class="mjx-mrow"><span id="MJXc-Node-48" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-49" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> là thấu kính phân kỳ.</p>
<p><span id="MathJax-Element-11-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math>"><span id="MJXc-Node-51" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-52" class="mjx-mrow"><span id="MJXc-Node-53" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-54" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> là thấu kính phân kỳ; <span id="MathJax-Element-12-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math>"><span id="MJXc-Node-56" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-57" class="mjx-mrow"><span id="MJXc-Node-58" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-59" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> là thấu kính hội tụ.</p>
<p><strong>Giải</strong></p>
<p>a) Ta có: <math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mn>1</mn><msub><mi>d</mi><mn>1</mn></msub></mfrac><mo>+</mo><mfrac><mn>1</mn><mrow><mi>d</mi><msub><mo>'</mo><mn>1</mn></msub></mrow></mfrac><mo>=</mo><mfrac><mn>1</mn><msub><mi>f</mi><mn>1</mn></msub></mfrac><mspace linebreak="newline"/></math></p>
<p>Vì <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>d</mi><mn>1</mn></msub><mo>=</mo><mo>∞</mo><mo> </mo><mo>⇒</mo><mi>d</mi><msub><mo>'</mo><mn>1</mn></msub><mo>=</mo><msub><mi>f</mi><mn>1</mn></msub></math></p>
<p>Mà </p>
<p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>l</mi><mo>=</mo><msub><mi>f</mi><mn>1</mn></msub><mo>+</mo><msub><mi>f</mi><mn>2</mn></msub><mo> </mo><mo>(</mo><mo> </mo><mi>F</mi><msub><mo>'</mo><mn>1</mn></msub><mo>=</mo><msub><mi>F</mi><mn>2</mn></msub><mo>)</mo><mspace linebreak="newline"/><mi>n</mi><mi>ê</mi><mi>n</mi><mo> </mo><msub><mi>d</mi><mn>2</mn></msub><mo>=</mo><mi>l</mi><mo>-</mo><mi>d</mi><msub><mo>'</mo><mn>1</mn></msub><mo>=</mo><msub><mi>f</mi><mn>2</mn></msub><mspace linebreak="newline"/><mfrac><mn>1</mn><msub><mi>d</mi><mn>2</mn></msub></mfrac><mo>+</mo><mfrac><mn>1</mn><mrow><mi>d</mi><msub><mo>'</mo><mn>2</mn></msub></mrow></mfrac><mo>=</mo><mfrac><mn>1</mn><msub><mi>f</mi><mn>2</mn></msub></mfrac><mspace linebreak="newline"/><mo>⇒</mo><mi>d</mi><msub><mo>'</mo><mn>2</mn></msub><mo>=</mo><mo>∞</mo></math></p>
<p><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>⇒</mo></math> Chùm tia ló cuối cùng là chùm tia ló song song.</p>
<p>b) - Trường hợp 1: <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub><mo>;</mo><mo> </mo><msub><mi>L</mi><mn>2</mn></msub></math> là thấu kính hội tụ (hình 30.4)</p>
<p><img class="wscnph" src="https://static.colearn.vn:8413/v1.0/upload/library/24022022/304-mpmOKO.jpg" width="368" height="204" /></p>
<p>-Trường hợp 2 : <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math>là thấu kính hội tụ; <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math><span id="MathJax-Element-10-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math>"><span id="MJXc-Node-46" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-47" class="mjx-mrow"><span id="MJXc-Node-48" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-49" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> là thấu kính phân kỳ. </p>
<p><img class="wscnph" src="https://static.colearn.vn:8413/v1.0/upload/library/24022022/305-bjkvXC.jpg" width="362" height="225" /></p>
<p> </p>
<p>- Trường hợp 3: <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>1</mn></msub></math> là thấu kính phân kỳ; <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math><span id="MathJax-Element-12-Frame" class="mjx-chtml MathJax_CHTML" style="box-sizing: border-box; margin: 0px; padding: 1px 0px; overflow-wrap: normal; word-break: break-word; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 18.08px; letter-spacing: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>L</mi><mn>2</mn></msub></math>"><span id="MJXc-Node-56" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-57" class="mjx-mrow"><span id="MJXc-Node-58" class="mjx-msubsup"><span class="mjx-base"><span id="MJXc-Node-59" class="mjx-mi"></span></span></span></span></span><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mn></mn></msub></math></span> là thấu kính hội tụ.</p>
<p><img class="wscnph" src="https://static.colearn.vn:8413/v1.0/upload/library/24022022/306-lG5g0A.jpg" width="364" height="194" /></p>
<p> </p>
<p> </p>
Hướng Dẫn Giải Bài 4 ( Trang 195 - SGK Vật Lí 11)
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Hướng Dẫn Giải Bài 4 ( Trang 195 - SGK Vật Lí 11)
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