A material kept at high temperature is seen to emit photons with energies of 0.3 eV, 0.5eV, 0.8 eV, 2.0 eV, 2.5 eV, and 2.8 eV. These are the only photon energies observed. It is now cooled down to a very low temperature so that it is not emitting photons anymore. If a beam of light with a continuous range of energies from 0.01 eV to 10 eV shines on the material, what photon energies in this beam will correspond to dark absorption lines?

1. 0.3 eV, 0.5 eV, 2.8 eV

2. 0.3 eV, 0.5 eV, 0.8 eV

3. 0.3 eV, 0.8 eV, 2.8 eV

4. 0.8 eV, 2.0 eV, 2.8 eV

5. 0.5 eV, 0.8 eV, 2.8 eV

6. 0.3 eV, 2.5 eV, 2.8 eV

What is the measurement of how fast an object moves relative to a reference point?

What is similar between metals and suspensions

Asteel tube (k=50 w/mk) of inner and outer diameter di = 20mm and do=26mm, respectively, is used to transfer heat from hot gases flowing over the tube (h-hot = 200w/m2k) to cold water flowing through the tube (h-cold = 8000 w/m2k). what is the cold-side overall heat transfer coefficient uc? to enhance heat transfer 16 straight fins of rectangular profile are installed longitudinally along the outer surface of the tube. the fins are equally spaced around the circumference of the tube, each having a thickness of 2mm and a length of 15mm. what is the corresponding overall heat transfer coefficient uc? *solve for uc in both cases*