Microwave ovens can have cold spots and hot spots due to standing electromagnetic waves, analogous to standing wave nodes and antinodes in strings (Fig. 20.32).

(a) The longer the distance between the cold spots, (1) the higher the frequency of the waves, (2) the lower the frequency of the waves, (3) the frequency of the waves is independent of this distance. Why?
(b) In your microwave the cold spots (nodes) occur approximately every 5.0 cm, but your neighbor€™s microwave produces them at every 6.0 cm. Which microwave operates at a higher frequency and by how much?

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