Two very thin lenses, each with focal length 20. cm, are placed ...

[Mimi]

Two very thin lenses, each with focal length 20. cm, are placed in contact. What is the focal length of this compound lens?
 
  A) 15. cm
  B) 10. cm
  C) 30. cm
  D) 40. cm
  E) 20. cm

Question 2

How much energy is carried by a photon of wavelength 660. nm?
 
  A) 1.46  10-48 J
  B) 3.01  10-19 J
  C) 6.63  10-34 J
  D) 5.39 eV
  E) 4.78  10-19 eV

[srodz]

Answer to Question 1

B

Answer to Question 2

B

[Mimi]

Thanks for the timely response, appreciate it

[helenmarkerine]

Excellent