Answer:
concave lens
Explanation:
it's concave lens because it diverges the ray/beam of light.
Answer:
1) 1.808 *10^8 vacancies per cm^3
2) 101,64ºC
Explanation:
You can use the following equation relating the number of vacancies with the energy required to produce them and the temperature:
![n_{v} =Ne^{\frac{-E}{K_{b}*T} }](https://tex.z-dn.net/?f=n_%7Bv%7D%20%3DNe%5E%7B%5Cfrac%7B-E%7D%7BK_%7Bb%7D%2AT%7D%20%7D)
Where N is the number atoms per unit of volume, you can calculate this number with the density of copper:
![8.96 \frac{g}{cm^{3} } *\frac{1 mole copper}{63.54 g } *\frac{6.023*10^{23} atoms }{1 mole} = 8.47*10^{22}atoms](https://tex.z-dn.net/?f=8.96%20%5Cfrac%7Bg%7D%7Bcm%5E%7B3%7D%20%7D%20%2A%5Cfrac%7B1%20mole%20copper%7D%7B63.54%20g%20%7D%20%2A%5Cfrac%7B6.023%2A10%5E%7B23%7D%20atoms%20%7D%7B1%20mole%7D%20%3D%208.47%2A10%5E%7B22%7Datoms)
And you can substitute all values in the equation:
![n_{v} =8.47*10^{22}atoms*e^{\frac{-20 000 cal}{6.023*10^{23}mol^{-1}*3.297*10^{-24}cal*k^{-1}*298.15K} }=1.808*10^{8}atoms](https://tex.z-dn.net/?f=n_%7Bv%7D%20%3D8.47%2A10%5E%7B22%7Datoms%2Ae%5E%7B%5Cfrac%7B-20%20000%20cal%7D%7B6.023%2A10%5E%7B23%7Dmol%5E%7B-1%7D%2A3.297%2A10%5E%7B-24%7Dcal%2Ak%5E%7B-1%7D%2A298.15K%7D%20%7D%3D1.808%2A10%5E%7B8%7Datoms)
Now you solve for temperature and and use n as 1000 times the value of before:
![T=\frac{-E}{k_{b}ln(n/N)} =\frac{-(2*10^{4}cal)}{(3.297*10^{24}calk^{-1})*ln(1.8083*10^{11}/8.47*10^{22})} =374.79 K = 101.64 C](https://tex.z-dn.net/?f=T%3D%5Cfrac%7B-E%7D%7Bk_%7Bb%7Dln%28n%2FN%29%7D%20%3D%5Cfrac%7B-%282%2A10%5E%7B4%7Dcal%29%7D%7B%283.297%2A10%5E%7B24%7Dcalk%5E%7B-1%7D%29%2Aln%281.8083%2A10%5E%7B11%7D%2F8.47%2A10%5E%7B22%7D%29%7D%20%3D374.79%20K%20%3D%20101.64%20C)