1. Charge vibrates linearly along the direction illustrated. This oscillating dipole emits transverse waves preferentially in what direction? Waves are transmitted equally in all directions

2.  sin (90 o   ) = (1) sin  (2) -sin  (3) cos  (4) -cos  (5) tan  (6) -tan 

3. The magnetron of a microwave horn generates a horizontally varying B-field and oscillating vertical E-field. We found which of the aluminum gratings below let the microwaves pass? 1 2

4. A) B) C) D) If waves A and B are superposed (that is, their amplitudes are added) the resultant wave is

5. Phase Phase refers to the relative position of the wave crests of two waves Phase difference 180 o or ½ “Out of phase” Phase difference 0 o “In phase”

6. The two waves shown are A) out of phase by 180 o B) out of phase by 90 o C) out of phase by 45 o D) in phase

7. Destructive interference occurs when the two waves arriving at the same point at the same time are 1) out of phase by 180 o 2) out of phase by 90 o 3) out of phase by 45 o 4) in phase 5) could be any of these

8. Imagine two light sources emitting waves of 1 meter wavelength in phase. The waves from these sources meet at a distant point. Wave 1 travels 2 m to reach the point; wave 2 travels 3 m. When the waves meet, they are A) out of phase by 180 o B) out of phase, but not by 180 o C) in phase

9. Answers to preceding multiple choice questions: See Lecture 24’s descriptions of an oscillating dipole! sin (90 o   ) = x / h x / h = cos  (3) cos   90 o -  2 The vertical strips act as antenna offering free electrons to be driven by the Vertical E-field…absorbing microwave energy. The horizontal strips are not effective antennas and let the microwaves pass through. C) B) out of phase by 90 o 1) out of phase by 180 o C) in phase