An optical engineering firm needs to ensure that the separation between two mirrors is unaffected by temperature changes. The mirrors are attached to the ends of two bars of different materials that a

Question

An optical engineering firm needs to ensure that the separation between two mirrors is unaffected by temperature changes. The mirrors are attached to the ends of two bars of different materials that are welded together at one end, as shown. The surfaces of the bars in contact are lubricated. The distance $ℓ$ does not change with temperature. $ℓ_{1}$ and $ℓ_{2}$ are the lengths of the bars, and $α_{1}$ and $α_{2}$ are their respective coefficients of linear expansion. Which of the following options is/are correct?

Source diagram 55

Options:(select one or more)

Answer:

C

Solution:

The mirror separation is the difference of the two bar lengths.
It stays fixed when both bars expand equally.
$ℓ_{1} α_{1} = ℓ_{2} α_{2}$
$\frac{ℓ _{1}}{ℓ _{2}} = \frac{α _{2}}{α _{1}}$

TestHub · Accepted Answer

The mirror separation is the difference of the two bar lengths. It stays fixed when both bars expand equally. ℓ 1 ​ α 1 ​ = ℓ 2 ​ α 2 ​ ℓ 2 ​ ℓ 1 ​ ​ = α 1 ​ α 2 ​ ​

Physics - Heat & Thermo Question with Solution | TestHub

Options:(select one or more)

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