23. Aircraft equipped with powerful radar units are forbidden from using them when parked on the ground near people. Explain why this is so.

25. What is different about our perceptions of the different frequencies within the visible light band of the EM spectrum?

29. What is blackbody radiation? In what ways does the radiation emitted by a blackbody change as its temperature increases?

33. Stars emit radiation whose spectrum is very similar to that of a blackbody. Imagine two stars identical in size, each of which is at the same distance from us. One of the stars appears reddish in color, while the other one looks distinctly bluish. Based on this information, what can you say about the relative temperatures of the two stars? Which is the hotter? How do you know?

35. Describe the greenhouse effect that is occurring in Earth's atmosphere.

37. Six blackbody radiators have temperatures and emitted powers as given. Rank these blackbodies according to their emitting surface areas from smallest to largest. Justify your rankings based on your knowledge of the physics of blackbodies.

Blackbody A: P = 6000 W; T = 50 K

Blackbody B: P = 6000 W; T = 10 K

Blackbody C: P = 20,000 W; T =30 K

Blackbody D: P = 50,000 W; T = 50 K

Blackbody E: P = 10,000 W; T = 10 K

Blackbody F: P = 50,000 W; T = 50 K