# The Pyrex glass mirror in the telescope at the Mount Palomar Observatory (the Hale telescope) has a diameter of 200 in. The most extreme temperatures ever recorded on palomar Mountain are - 10°C and 50°C, Determine the maximum change in the diameter of the mirror.

28 Points
3 years ago
diameter =d=200 inc
change in temperature =$\Delta$T=50°-(-10°) = 60°C
cofficient of expansion for pyrax glass=$\alpha$=3.2×10^-6/C°
FORMULA:
$\Delta$L=$\Delta$$\alpha$×d
=60°C × 3.2×10^-6/C°× 200 inc
=38400 × 10^-6 inc
= 0.0384 inc

so, maximum increase in diameter is 0.0384 inc and total diameter after increase in temperature is = 200inc + 0.0384inc
= 200.0384 inc