Phys 4, Section 2                  Quiz 9                                  Apr 4, 2002

1. The units of the Poynting vector are
A) watts         B) joules         C) watts/m²         D) J/m²          E) watts/s

2. The time average of cos ωt is
A) 0         B) ½         C) 1         D) 2

3. The time average of sin² ωt is
A) 0         B) ½         C) 1         D) 2

4. More electromagnetic momentum is imparted to a surface when an e-m wave
striking it is completely
A) reflected                            B) absorbed
C) same in both cases             D) e-m wave has no momentum

5. In an e-m wave, the E-field is at the top of its vertical motion when the B-field
is at the extreme west of its horizontal motion. The direction of propagation is
A) north         B) south         C) east         D) west

6. The average wavelength of visible light is about
A) 0.5 micron         B) 0.5 mm         C) 0.5 nm             D) 0.5 m

7. The ratio E/B for an e-m wave in space is
A) 1/c         B) n         C) c         D) ε₀          E) 1/n

8. To produce TIR, the light must approach the interface from the side with the
A) larger index         B) smaller index          C) doesn’t matter

9. The value of the critical angle θ_c is given by
A) n₁/n₂         B) n₂/n₁         C) asin (n₂/n₁)         D) asin (n₁/n₂)     E) atan (n₂/n₁)

10. If a beam of light moving downward at an angle traverses two media with a
horizontal interface, the transmitted angle will be larger than the reflected angle if
the lower index, compared to the upper index, is
A) smaller         B) larger         C) either case         D) never happens

Answers: 1-c, 2-a, 3-b, 4-a, 5-b, 6-a, 7-c, 8-a, 9-c, 10-a 

Last modified on April 04, 2002