Suppose that the Department of Energy develops a new reversible ...

[ericka1]

Suppose that the Department of Energy develops a new reversible engine that has a coefficient of performance (COP) of 4.0
 
  when operated as a refrigerator and a COP of 5.0 when operated as a heat pump. What is its thermal efficiency when operated as a heat engine doing work?
  A) 20 B) 10 C) 45 D) 80 E) 25

Question 2

For a certain metal, light of frequency 7.24  10-14 Hz is just barely able to dislodge photoelectrons from the metal. (h = 6.626  10-34 J  s, 1 eV = 1.60  10-19 J, e = 1.60  10-19 C)
 
  (a) What will be the stopping potential if light of frequency 8.75  10-14 Hz is shone on the metal?
  (b) What is the work function (in electron-volts) of this metal?

[jlaineee]

Answer to Question 1

A

Answer to Question 2

(a) 0.625 V (b) 3.00 eV

[ericka1]

Thanks

[jlaineee]

Welcome