• 9702 November 2018 Paper 12 Worked Solution | A-Level Physics

1 A                  11 D                21 D                31 C

2 B                  12 C                22 D                32 D

3 B                  13 A                23 B                33 A

4 A                  14 C                24 A                34 A

5 A                  15 D                25 D                35 D

6 C                  16 A                26 D                36 B

7 B                  17 A                27 A                37 B

8 B                  18 B                28 B                38 C

9 B                  19 A                29 A                39 C

10 D                20 D                30 C                40 A

28 - Ans: B.
What happens when waves pass through a gap equal to their wavelength?



29 - Ans: A.
Two sources of microwaves P and Q produce coherent waves with a phase difference of 180.  The waves have the same wavelength λ.